LIBRARY 


UNIVERSITY  OF  CALIFORNIA. 


Class 


THE  LETTERS  OF 
BERZELIUS  AND  SCHONBEIN 


THE    LETTERS 

OP 

JONS  JAKOB   BERZELIUS 


At 

AND 


CHRISTIAN  FRIEDRICH  SCHONBEm 

1836-1847 


EDITED   BY 

GEOKG  W.  A.  KAHLBAUM 

BALE 
TRANSLATED   BY 

FRANCIS  V.  DARBISHIRE,  PH.D. 

AND 

N.  V.  SIDGWICK 


WILLIAMS    AND    NORGATE 

14  HENRIETTA  STREET,  COVENT  GARDEN,  LONDON 

20  SOUTH  FREDERICK  STREET,  EDINBURGH 

AND  7  BROAD  STREET,  OXFORD 

1900 


PRINTED  BY 

NEILL  AND  COMPANY,  LIMITED 
EDINBURGH 


SENEKAi. 


EDITOR'S  PREFACE 


FOR  some  time  past  I  have  been  engaged  on  the  bio- 
graphy of  Christian  Friedrich  Schonbein,  the  discoverer 
of  ozone  and  the  inventor  of  guncotton,  formerly  professor 
of  chemistry  and  physics  at  the  University  of  Bale,  the 
hundredth  anniversary  of  whose  birth  will  be  celebrated 
on  the  18th  of  October  of  next  year.  Schonbein's  family 
have  assisted  me  in  the  kindest  manner  in  this  work; 
they  have  placed  at  my  disposal  the  whole  mass  of  papers 
which  this  indefatigable  physical  chemist  left  behind, 
and  the  many  hundreds  of  letters  which  he  received. 

Such  writings,  far  more  than  the  sifted  published 
results,  give  us  a  true  insight  into  the  thoughts  of  the 
writer,  and  enable  us  to  understand  the  workings  of  his 
mind.  We  have,  moreover,  a  never-failing  series  of 
incidental  allusions  to  the  conditions,  the  manner  and 
the  difficulties  of  sending  letters,  the  calculation  of  the 
cost  of  postage,  and  the  time  taken  in  travelling ;  and 
thus  there  develops  almost  insensibly  before  our  eyes  a 
picture  of  a  bygone  age,  which  forms  a  background  to 
the  image  of  the  writer  himself.  We  are  continually 
meeting  with  casual  remarks,  begotten  of  the  confidence 
of  the  moment,  which  reveal  to  us  ever  new  traits  of 
character,  and  seem  to  bring  the  writer  before  us  in  person, 
and  to  turn  into  tangible  figures  those  who  before  were 
to  us  often  only  names  and  shadows. 

A 

101714 


6  PREFACE 

The  letters  which  Schonbein  left  behind  cover  a  period 
of  nearly  fifty  years.  They  begin  in  the  year  1820  and 
extend  to  his  death  in  1868.  Among  their  writers  are 
to  be  found  the  most  illustrious  men  of  the  time.  The 
greatest  of  all  is  Faraday :  there  are  about  seventy  letters 
from  him  to  Schb'nbein,  and  as  many  more  from  Schonbein 
in  reply ;  then  come  Grove,  Graham,  Sir  John  Herschel, 
and  a  series  of  other  English  men  of  science.  Among 
Germans  there  is  in  the  first  place  Wilhelm  Eisenlohr  of 
Karlsruhe,  the  physicist,  who  furnishes  more  than  a 
hundred  letters ;  then  Schelling,  Schonbein's  great  teacher, 
with  whom  he  kept  up  a  steady  intercourse  until  his 
death ;  Liebig  with  fifty  letters,  and  Pettenkof er  with  as 
many  more,  and  Wohler  with  about  thirty ;  then  Martius, 
Jolly,  Kobell,  Steinheil  of  Munich,  Magnus,  Mitscherlich, 
and  Poggendorff  of  Berlin,  Erdmann  of  Leipsic,  Muncke 
of  Heidelberg,  Hugo  Mohl  of  Tubingen,  Dingier  of 
Augsburg,  the  well-known  editor  of  the  Polytechmcal 
Journal,  in  whose  factory  young  Schonbein  had  once 
worked,  and  many  others,  particularly  among  his  Swabian 
countrymen.  To  these  must  be  added  a  series  of  Swiss 
scientific  men :  Auguste  de  la  Rive,  Marignac,  Brunner, 
and  Agassiz ;  while  among  Frenchmen  we  have  Henri 
Sainte-Claire-Deville,  Dumas,  Scoutetten  of  Metz,  etc. 
Finally  there  are  nine  letters  extending  from  1837  to 
1847  from  Jakob  Berzelius. 

The  9th  of  August  of  this  year  [1898]  was  the  fiftieth 
anniversary  of  the  death  of  Berzelius,  who  was  exactly 
twenty  years  older  than  Schonbein,  and  died  twenty  years 
before  him.  This  anniversary,  as  is  right,  is  not  to  be 
allowed  to  pass  unnoticed ;  it  is  to  be  celebrated  in  Stock- 
holm on  the  9th  of  October,  and  I  should  be  glad  to  be 
able  to  assist  in  the  celebration  in  some  slight  degree,  by 
laying  the  following  pages  as  a  modest  tribute  on  the  tomb 
of  the  great  master. 


PEEFACE  7 

Prof.  Henrik  G.  Soderbaum  of  Stockholm,  a  Fellow  of 
the  Royal  Swedish  Academy  of  Sciences,  has  already 
published  at  my  suggestion,  in  the  series  of  Monographs 
on  the  History  of  Chemistry  which  I  am  editing,  a 
number  dedicated  to  the  memory  of  Berzelius,  a  subject 
with  which  he  is  peculiarly  fitted  to  deal ;  but  I  should 
wish  to  contribute  my  mite  personally,  by  giving  to  the 
public  on  the  day  of  the  celebration  in  Stockholm  the 
correspondence  between  Berzelius  and  Schonbein  which 
has  been  placed  in  my  hands. 

What  I  have  to  offer  contains  no  startling  novelties ; 
no  explanations  that  are  to  revolutionize  our  previous 
theories  can  be  derived  from  these  letters.  But  to  prove 
what  I  have  said  of  the  importance  of  letters  as  the 
original  sources  of  the  history  of  the  development  of 
certain  definite  ideas,  and  of  the  knowledge  of  personalities 
which  we  can  derive  from  them,  it  is  only  necessary  to 
compare  the  letters  which  Berzelius  wrote  to  Schonbein 
with  those  which  he  wrote  to  Liebig  \  for  even  these  few 
pages  substantiate  to  the  fullest  extent  the  claims  which 
I  have  put  forward. 

And  yet  how  wholly  different  were  the  lines  of  research 
which  the  two  men  followed.  Berzelius,  a  master  of  the 
methods  of  quantitative  analysis,  has  his  attention  always 
centred  on  the  final  product,  considered  in  its  quantitative 
relations  :  Schonbein,  for  whom  this  branch  of  chemical 
research  possesses  hardly  any  interest,  is  far  more  bent  on 
acquiring  from  characteristic  indications  the  means  of 
disentangling  the  course  of  the  reactions.  While  Ber- 
zelius' mind  embraced  the  whole  range  of  chemical  know- 
ledge, Schonbein  concentrated  his  attention  on  a  narrowly 
contracted  field,  but  yet  regarded  that  field  from  com- 
manding points  of  view ;  and  both  took  an  equal  interest 
in  observing  the  interconnection  of  chemical  and  electrical 
energy.  The  younger  man  from  the  beginning  looked  up 


8  PKEFACE 

with  honest  reverence  to  his  great  master  in  Stockholm, 
while  the  latter,  gradually  convinced  of  the  peculiar  gifts 
of  his  junior,  ended  by  proclaiming  with  no  uncertain 
voice  the  importance  of  his  investigations;  the  one,  to 
use  Schonbein's  own  words,  "  with  his  ten  talents  gaining 
ten  more,  while  the  other  none  the  less  strove  to  put  his 
single  talent  out  at  usury."  These  two  men  have  filled 
many  a  page  in  the  history  of  our  science,  often  with  im- 
perishable writings,  and  to  these  their  letters  serve  as  a 
commentary.  And  I  am  grateful  in  no  small  degree  to  the 
Royal  Swedish  Academy  of  Sciences  at  Stockholm,  and  to 
their  permanent  secretary,  Prof.  G.  Lindhagen,  for  their 
great  kindness  and  liberality  in  handing  over  to  me  for 
publication  the  letters  of  Schonbein  to  Berzelius,  which 
are  in  the  possession  of  the  Academy,  to  which  the  letters 
of  Berzelius  always  have  immediate  reference.  I  was 
thus  enabled  to  do  what  is  seldom  possible  in  such  a  case, 
namely,  to  give  both  sides  of  the  correspondence  at 
once. 

I  trust  that  this  little  book  will  be  favourably  received ; 
but  at  all  events  the  two  men  whose  words  it  contains 
will  secure  for  it  a  hearing. 

GEORG  W.  A.  KAHLBAUM. 


STEINABAD,  BLACK  FOREST, 

1st  September  1898. 


NOTE  BY  THE  TRANSLATORS, 


WE  have  included  in  this  translation  two  letters  of 
Schonbein's  (of  12th  February  and  29th  March  1847), 
and  also  a  paper  of  Schonbein's,  "On  various  chemical 
states  of  oxygen,"  which  are  not  in  the  German  edition. 
They  were  discovered  in  January  1899  (after  the  latter 
had  been  published),  together  with  about  200  other 
letters  addressed  to  Berzelius,  in  the  Berzelius  Museum 
at  Stockholm,  by  Herr  Lindstrom.  They  were  placed 
in  the  University  Library  at  Bale  for  a  time,  in  order 
that  we  might  obtain  copies  of  them,  and  we  wish  to 
express  our  thanks  to  the  authorities  of  the  Library 
for  their  kindness  in  permitting  us  to  do  so.  Schon- 
bein's paper,  which  has  never  before  appeared  in  print, 
is  of  interest  both  generally  and  as  throwing  light  on 
the  views  which  he  expresses  in  his  letters  to  Berzelius. 

F.  V.  D. 

1ST.  V.  S. 


OF  THE 

|  UNIVERSITY   '? 

OF 


CONTENTS. 


PAGE 

Editor's  Preface, 5 

Note  by  the  Translators,           .....  9 

I.  Schonbein  to  Berzelius,  22nd  April  1836,          .        .  18 

II.  Berzelius  to  Schonbein,  4th  May  1837,     ...  24 

III.  Schonbein  to  Berzelius,  14th  October  1838,      .        .  28 

IV.  Berzelius  to  Schonbein,  13th  November  1838,  .        .  32 
V.  Schonbein  to  Berzelius,  28th  March  1839,         .         .  34 

VI.  Berzelius  to  Schonbein,  18th  September  1840,  .         .  37 

VII.  Schonbein  to  Berzelius,  llth  September  1840,  .         .  39 

VIII.  Berzelius  to  Schonbein,  3rd  November  1840,     .        .  42 

~tX.  Schonbein  to  Berzelius,  23rd  February  1844,    .        .  43 

X.  Schonbein  to  Berzelius,  14th  April  1844,          .        .  45 

XL  Berzelius  to  Schonbein,  16th  May  1844,           .         .  59 

£11.  Schonbein  to  Berzelius,  15th  January  1845,      .         .  62 

XIII.  Berzelius  to  Schonbein,  14th  February  1845,    .         .  67 

XIV.  Schonbein  to  Berzelius,  1st  March  1845,           .        .  69 
XV.  Schonbein  to  Berzelius,  22nd  March  1845,        .        .  73 


12  CONTENTS 

PAGE 

XVI.  Schonbein  to  Berzelius,  30th  September  1845,         .  79 

XVII.  Schonbein  to  Berzelius,  5th  March  1846,        .        .  81 

XVIII.  Schonbein  to  Berzelius,  20th  June  1846,          .        .  86 

XIX.  Berzelius  to  Schonbein,  18th  November  1846,          .  88 

XX.  Schonbein  to  Berzelius,  12th  February  1847,  .        .  91 

XXI.  Berzelius  to  Schonbein,  12th  March  1847,       '.        .  95 

XXII.  SchSnbein  to  Berzelius,  29th  March  1847,       .        .  99 

Appendix.     On  various  chemical  states  of  oxygen,  106 


THE  LETTERS  OF 

BERZELIUS  AND  SCHONBEIN 


SCHONBEIN  spent  the  winter  of  1827-28  in  Paris,  whither 
he  had  gone  like  so  many  men  of  various  nationalities 
at  that  time  to  complete  his  studies.  He  had  been  a 
science  master  in  a  school  at  Epsom  and  had  acquired 
a  thorough  knowledge  of  English.  About  this  time  a 
French  edition  of  Berzelius'  Ldrbok  i  Kemien  was  pub- 
lished. In  an  undated  letter  which  I  have  before  me 
in  draft  only,  but  which  was  probably  written  in 
November  1827,  Schonbein  writes  to  Koller,  a  friend 
and  countryman  of  his,  who  was  a  bookseller  in  London, 
as  follows :  "  Now  as  to  a  proposal  which  I  have  no 
doubt  you  will  accept.  You  are  probably  aware  that 
among  chemists  Berzelius  is  one  of  the  leading  lights  of 
the  age,  and  that  his  textbook  of  chemistry,  which,  how- 
ever, will  not  be  completed  before  next  year,  is  a  classical 
work.  Three  volumes  have  already  appeared ;  the  fourth 
and  concluding  one  is  expected  soon.  Now  England 
actually  does  not  at  present  possess  such  a  book ;  and 
since  Berzelius  is  undoubtedly  held  in  great  esteem  in 
this  country  and  his  book  is  superior  to  any  in  Europe 
in  originality  and  exhaustive  treatment  of  its  subject,  a 


14  LETTEES  OF  BEBZELIUS 

friend  of  mine,  an  English  chemist  here,  and  I,  thought 
it  would  be  well  worth  our  while  to  undertake  a  transla- 
tion of  it  into  English.  We  are  quite  convinced  that 
such  a  publication  would  prove  a  financial  success  to  the 
publisher.  Therefore  I  offer  you  the  translation,  and  in 
the  event  of  your  accepting  it  I  enclose  a  brief  announce- 
ment which  I  think  it  would  be  desirable  to  print  in  some 
widely-read  paper,  for  the  purpose  of  keeping  others 
from  a  similar  undertaking  and  also  of  bringing  it  under 
the  notice  of  the  public.  Please  let  me  know  your  final 
decision  by  return  of  post,  for,  should  you  not  feel  inclined 
to  undertake  it,  we  shall  have  to  turn  elsewhere.  It  is 
no  doubt  an  immense  task,  but  by  no  means  a  hazardous 
one,  and  certainly  more  profitable  than  the  bookselling 
business. 

"My  time  is  at  present  so  taken  up  that  I  must 
content  myself  with  sending  you  my  kindest  regards. 
— C.  E.  S." 

That  Schonbein  was  really  in  earnest  in  his  intention 
of  translating  Berzelius'  book  into  English  is  shown  by 
the  fact  that  he  enclosed  an  announcement  of  the  proposed 
translation  for  the  daily  papers. 

We  can  also  see  what  special  object  Schonbein  had 
in  approaching  so  great  a  task.  Sprung  from  humble 
surroundings,  he  was  forced  to  gain  his  own  livelihood ; 
and  in  addition  to  the  strong  liking  he  then  had  for 
teaching,  for  which,  however,  he  failed  to  find  a  promising 
field  in  Paris,  he  devoted  himself  keenly  to  literary 
pursuits.  Thus,  in  November  1827,  almost  at  the  time 
when  he  formed  the  project  of  translating  Berzelius,  he 
wrote  to  Eriedrich  Perthes  of  Gotha,  with  whom  he  was 
already  acquainted  through  his  son  and  nephew,  offering 
to  translate  into  German,  from  his  shorthand  notes,  the 
lectures  on  physics  given  by  Gay-Lussac  at  the  Sorbonne, 
and  to  entrust  them  to  him  for  publication.  But  this 


AND  SCHONBEIN  15 

and  other  works  were  comparatively  unimportant  enter- 
prises, whereas  the  translating  of  the  solid  200  sheets  of 
Berzelius'  treatise,  and  moreover  into  English,  a  foreign 
language,  was  certainly  a  stupendous  task. 

The  motives  which  induced  him  to  undertake  so  great 
a  work  we  learn  from  a  letter,  which  I  possess  only  as  an 
undated  draft,  which  he  wrote  at  about  this  time  to  his 
friend  and  countryman  Heldenmeier,  who  also  was  a 
schoolmaster  at  Epsom.  In  this  letter  he  declines  for 
the  time  being  an  offer  to  assist  in  founding  a  school  in 
his  "beloved  Switzerland,"  and  writes  respecting  it  as 
follows  :  "  Let  me  tell  you  why ;  four  weeks  ago  I  formed 
a  fixed  determination  of  [going]  to  Berzelius  at  Stockholm 
towards  the  end  of  next  [year  ?]  to  complete  my  studies 
under  this  consummate  master  of  chemical  science ;  this 
plan  leads  to  others  ;  means  must  be  procured  for  its  real- 
ization ;  and  it  is  a  translation  of  Berzelius'  unique  work 
that  is  to  procure  them ;  a  part  of  this  work  has  already 
appeared  and  the  remainder  is  still  in  the  press.  With 
this  end  in  view  I  have  joined  with  a  young  Englishman, 
with  whom  I  shall  soon  enter  upon  the  work,  which  will 
occupy  us  six  months  at  the  very  least.  So  far  we  know 
of  no  publisher,  but  we  do  not  doubt  that  we  shall  be 
able  to  find  one,  for  the  publication  cannot  be  otherwise 
than  lucrative.  Lee  this,  however,  remain  a  secret 
between  us.  I  do  not  intend  to  return  to  England  before 
the  lectures  are  over,  for  this  would  be  foolish.  Nor 
shall  I  stay  long.  Should  our  plans  be  realized  I  shall 
soon  be  sailing  towards  Sweden,  where  I  propose  to  spend 
at  least  six  months.  But  after  that  .  .  .  1 " 

Nothing  came  of  the  translation  of  Gay-Lussac's 
lectures ;  for  Perthes  wrote  on  December  the  1st  declining, 
though  in  the  most  courteous  terms,  to  publish  them, 
owing  to  other  more  pressing  business,  the  details  of 
which  he  specifies;  a  similar  fate  befel  the  English 


16  LETTERS  OF  BERZELIUS 

translation  of  Berzelius'  textbook.  The  publisher  could 
not  persuade  himself  to  undertake  the  work,  which, 
though  attended  with  a  considerable  outlay,  would  un- 
questionably have  resulted  in  pecuniary  gain.  The 
consequence  was  that  England  had  to  dispense  with  a 
translation  of  Berzelius'  great  and  at  that  time  unsurpassed 
work,  while  Schonbein,  foiled  in  his  plan  for  obtaining 
the  necessary  supplies,  had  to  relinquish  his  scheme  of 
concluding  his  studies  under  "  the  consummate  master 
of  chemical  science." 

It  is  no  doubt  an  idle  task  to  imagine  what  might  have 
happened  if  matters  had  fallen  out  otherwise;  but  we 
cannot  resist  a  feeling  of  the  keenest  regret  that  it  was 
not  granted  to  Schonbein  to  turn  his  attention  to  quanti- 
tative work  as  well  under  the  influence  of  the  powerful 
personality  of  Berzelius,  and  our  disappointment  that  a 
publisher's  lack  of  public  spirit  should  have  prevented 
Schonbein  from  making  this  pilgrimage,  is  even  more 
acute  than  that  caused  by  the  events  which  hindered 
Liebig  from  working  under  this  great  chemist's  direction. 
Berzelius  and  Schonbein  were  so  unlike  in  character  that 
they  could  not  but  have  been  drawn  together;  and 
Schonbein  would  have  supplemented  Berzelius  far  more 
fully  than  Liebig  would  have  done.  Once  again  we 
come  across  the  name  of  Berzelius  about  this  time  in  a 
manuscript  of  Schonbein's.  A  small  diary  begun  on  the 
21st  of  January  1828  in  Paris,  the  last  entry  of  which 
dates  from  the  10th  of  March,  gives  us  a  clue  to  the 
reading  to  which  Schonbein  devoted  himself  at  this  period. 
A  large  part  of  this  book,  fifteen  pages  out  of  thirty, 
is  occupied  by  an  abstract  of  Berzelius'  paper  on  indigo.1 
It  is  evident  therefore  that  Schonbein  was  not  then 
penetrated  "by  that  almost  unconquerable  aversion  to 

1  "Recherches  sur  1'Indigo,"  Annal.  de  Chimie^  vol.  xxxvi. 
(1827)  pp.  310  and  350. 


AND  SCHONBEIN  17 

anything  relating  to  organic  life  "  which  he  confessed  to 
himself  in  later  years.1 

It  is  quite  typical,  however,  of  Schonbein  that  this 
paper  of  Berzelius'  is  preceded  by  a  summary  of  a  research 
by  Faraday2  on  the  behaviour  in  vacuo  of  a  crystal  of 
camphor,  slightly  cooled,  as  compared  with  that  of 
powdered  camphor. 

Not  long  afterwards  negotiations  were  entered  into 
with  Schonbein,  who  had  just  returned  to  England, 
through  Dr.  Engelhart,3  who  was  then  living  in  Paris  and 
had  refused  a  call  to  Bale,  and  they  resulted  in  Schonbein 
arriving  at  Bale  in  November  1828,  and  taking  over,  in 
the  first  instance  only  provisionally,  the  professorship  of 
Peter  Merian.4 

In  1835  and  1836  Schonbein  delivered  a  course  of 
lectures  before  the  Scientific  Institute  of  Bale,5  "which 
for  the  most  part  treated  of  electro-chemical  phenomena." 
Among  these  his  attention  was  particularly  directed  to 
that  behaviour  of  iron  which  he  termed  its  passivity.  A 
summary  of  these  communications  appeared  in  Poggen- 
dorff's  Annalen,  in  the  Bibliotheque  Universelle  and  in 
the  Philosophical  Magazine  6 :  and  it  is  thoroughly  charac- 

1  Schonbein,  Menschen  und  Dinge.     Mittheilungen  aus  dem 
Reisetagebuch  eines  Naturforschers.     Stuttgart  und  Hamburg 
(1855)  p.  117. 

2  "  On  the  existence  of  a  limit  to  vaporization,"  Phil.  Trans. 
(1826)  p.  484. 

3  Johann  Friedrich  Philipp   Engelhart,  Ph.D.,  professor  of 
chemistry  at  the  District  Agricultural  and  Industrial  School  at 
Nuremberg,  was  born  in  1797  at  Wildenstein,  near  Crailsheim, 
in  Wurtemberg,  and  died  at  Nuremberg  in  1837. 

4  Peter  Merian,  professor  of  physics  and  chemistry  at  Bale 
from  1827  to  1835,  born  at  Bale  in  1795  and  died  in  1883. 

5  "Bericht  uber  die  Verliandlungen  der  Naturforschenden 
Gesellschaft,"  in  Bale,  from  August  1835  to  July  1836.     Part  2. 
Bale  (1836)  p.  71. 

6  Poggend.  Annal,  vol.  xxxvii.  pp.  390  and  590  ;  vol.  xxxviii. 


18  LETTEES  OF  BEEZELIUS 

teristic  of  Schb'nbein  that  the  report  in  the  transactions 
is  not  written  by  himself,  but  by  his  countryman  and 
friend  Fischer,1  professor  of  philosophy,  in  a  paper 
occupying  twenty-six  pages,  entitled  :  "  Account  of  Pro- 
fessor Schonbein's  experiments  on  the  behaviour  of  iron 
towards  oxygen."  2 

It  is  these  experiments  which  form  the  subject  of 
Schonbein's  first  letter  to  Berzelius,  dated  22nd  of  April 
1836.  The  letter  is  as  follows  :— 


Schbnbein  to  Berzelius 

BALE,  22nd  April  1836. 

DEAR  SIR, 

It  is  only  your  well-known  kindness,  and  a 
hope  which  I  entertain  that  what  I  have  to  com- 
municate may  not  be  wholly  without  interest  to  you, 
which  encourage  me,  though  a  perfect  stranger,  to 
trouble  you  with  a  letter  from  so  great  a  distance. 

For  several  months  I  have  been  occupied  with  the 
more  accurate  determination  of  the  behaviour  of 
certain  metals,  particularly  iron,  under  various  con- 
ditions,  in  the  presence  of  nitric  acid.  My  work  has 

p.  444 ;  [vol.  xxxix.  p.  137]  (1836).  Bibl  univ.,  vol.  iii.  p. 
387  ;  vol.  v.  p.  177  (1836).  Phil.  Mag.,  vol.  ix.  pp.  53  and  [259] 
(1836).  The  passages  in  brackets  were  printed  after  the  Bale 
Keport. 

1  Friedrich  Fischer,  professor  of   philosophy  at  Bale  from 
1832  to  1853,  born  in    1801    at    Honau,   Black   Forest,  in 
Wurtemberg,  and  died  in  1853  at  Winnenden  in  the  Neckar 
district. 

2  Easier  Bericht,  vol.  i.,  part  2  (1836),  p.  72. 


AND  SCHONBEIN  19 

not  been  altogether  without  results.  I  have  observed 
certain  new  phenomena  which  can  hardly  fail, 
especially  from  an  electro-chemical  point  of  view,  to 
attract  the  attention  of  scientific  chemists.  They  are 
essentially  as  follows:  If  the  end  of  an  ordinary 
iron  wire  of  any  size  is  heated  in  a  spirit  lamp  until 
its  surface  has  become  blue,  and  is  then  put  in  nitric 
acid  of  specific  gravity  about  1/35,  neither  the  heated 
nor  the  other  end  of  the  wire  is  attacked.  Indeed, 
the  acid  can  be  heated  almost  to  its  boiling  point 
before  it  acts  on  the  metal,  although  it  attacks 
ordinary  iron  even  when  cold.  A  similar  behaviour 
is  shown  by  iron  filings  which  have  been  heated  only 
for  a  few  seconds,  that  is,  until  they  have  assumed  a 
blue  colour.  Now  it  is  remarkable  that  the  protec- 
tive power  of  the  heated  end  seems  to  extend  through 
any  length  of  wire,  however  great.  I  took  a  wire 
50  feet  long  and  a  line  thick,  heated  one  end  for  a 
distance  of  not  more  than  a  few  lines,  and  put  first 
this  end  and  then  the  other  into  acid  of  the  above- 
mentioned  strength.  Under  these  circumstances  no 
part  of  the  wire  was  attacked,  even  when  its  whole 
length  was  allowed  to  lie  in  the  acid.  In  order  to 
obtain  a  reaction  it  was  necessary  to  heat  the  liquid 
at  least  to  70°.  I  performed  similar  experiments 
with  iron  rods  of  a  considerable  size,  and  always 
obtained  the  same  result.  Another  remarkable  fact 
is  this :  An  iron  wire  which  has  thus  been  protected 
against  the  action  of  nitric  acid  can  bring  another 
iron  wire  into  the  same  neutral  condition  merely  by 
contact  (which  need  only  last  for  a  moment,  below 


20  LETTEES  OF  BEEZELIUS 

the  surface  of  the  liquid).  To  convince  yourself  of 
this  extraordinary  phenomenon,  take  an  iron  wire, 
one  end  of  which  has  been  tempered  by  heating. 
Bring  the  unheated  end  into  close  contact  with  one 
end  of  another  ordinary  iron  wire.  If  you  now  put 
first  the  heated  end  of  the  first  wire  and  then  the 
other  end  of  the  second  wire  into  the  acid,  the  latter 
will  not  be  attacked  by  it,  even  if  the  contact  between 
the  two  wires  is  destroyed.  The  second  wire,  having 
thus  become  passive,  can  communicate  the  condition 
to  a  third,  and  this  to  a  fourth,  and  so  on,  provided 
that  the  wires  are  brought  into  contact  within  the 
liquid  in  the  manner  described.  In  order  to  prevent 
any  misunderstanding  as  to  this  second  method  of 
rendering  an  iron  wire  inactive,  I  give  a  detailed 
account  of  the  way  in  which  the  experiment  is  to  be 
carried  out.  The  ordinary  wire,  which  has  thus  been 
made  indifferent  to  nitric  acid,  and  which  for  the 
sake  of  simplicity  I  will  call  "  secondarily  indifferent," 
is  taken  out  of  the  acid,  and,  at  any  point  which  has 
not  been  immersed,  brought  into  contact  with  another 
iron  wire.  The  end  of  the  secondarily  indifferent 
wire  is  then  placed  in  the  acid ;  and  finally  the  end 
of  the  other  wire.  Both  wires  now  remain  passive  in 
the  liquid,  always  supposing  that  the  temperature 
does  not  rise  above  70°.  For  the  sake  of  complete- 
ness I  must  add  that  an  iron  wire  which  has  been 
immersed  in  nitric  acid  of  specific  gravity  1-5  is  like- 
wise indifferent  to  the  acid  of  specific  gravity  1'36. 
A  third  phenomenon  of  interest  is  this :  if  an  iron 
wire,  which  has  been  made  indifferent  to  nitric  acid 


AND  SCHONBEIN  21 

in  any  of  the  ways  described,  is  placed  in  the  acid,  it 
is  again  attacked  by  it  if  brought  into  contact  with 
any  metal,  even  iron  itself,  which  is  actually  being 
dissolved  by  the  acid.  The  indifferent  wire  can,  how- 
ever, be  made  active  even  if  the  part  projecting  above 
the  liquid  (which  may  be  of  any  desired  length)  is 
brought  into  contact  with  the  similarly  projecting 
part  of  the  active  wire.  For  example  in  the  accom- 
panying figure1  let  a  b  be  the  vessel  containing  the 
nitric  acid,  c  d  the  indifferent,  and  e  f  the  active  wire. 
If  now  the  point  c  of  the  wire  c  d  is  brought  into 
contact  with  the  point  e  of  e  /,  the  immersed  portion 
of  c  d  at  once  becomes  active,  as  also  happens  if  / 
touches  d.  The  same  thing  occurs  likewise  if  c  is 
connected  with  d  by  any  metallic  wire. 

If  the  nitric  acid  is  very  dilute  none  of  these 
phenomena  happen.  After  arriving  at  these  results 
I  was  curious  to  see  how  an  iron  wire  would  behave 
in  nitric  acid  if  it  was  made  the  positive  pole  of  a 
voltaic  circuit.  My  experiments  on  this  point  have 
led  to  the  following  results.  If  the  negative  pole  of 
a  cup  apparatus  of  fifteen  elements  is  connected  with 
nitric  acid  of  specific  gravity  1-35  by  means  of  a 
platinum  wire,  and  one  end  of  a  common  iron  wire, 
of  which  the  other  is  attached  to  the  positive  pole,  is 
plunged  in  the  acid,  this  wire  remains  perfectly  in- 
active and  possesses  generally  all  the  properties  of 
the  wires  of  which  I  have  spoken  above.  Thus  a 
wire  of  this  kind  when  separated  from  the  positive 
pole  is  not  attacked  by  ordinary  nitric  acid.  But  if 
1  There  is  no  figure  in  the  letter. 


22  LETTEES  OF  BEEZELIUS 

the  circuit  is  not  closed  exactly  in  the  order  I  have 
described,  the  nitric  acid  acts  on  the  wire  in  the 
usual  chemical  manner.  If  an  iron  wire  which  has 
in  any  way  been  made  indifferent  is  connected  with 
the  negative  pole  of  a  battery,  it  is  instantly  attacked 
by  the  acid  with  violence.  But  the  most  remarkable 
fact  of  all,  a  fact  which  no  one,  so  far  as  I  know,  has 
ever  observed,  is  this.  The  positive  iron  wire  is  not 
only  not- acted  on~ky  the  acid,  but  it  is  not  even 
oxidized  by  the  oxygen  which  is  set  free  at  its  surface 
by  the  decomposition  of  the  water,  which  should 
occur  according  to  the  accepted  theory.  The  oxygen 
appears  as  a  gas  on  the  iron  just  as  it  does  on  a  wire 
of  silver  or  platinum,  and  the  metallic  surface  is  not 
altered  in  the  smallest  degree.  This  liberation  of 
oxygen  on  the  iron  wire  occurs  in  the  most  dilute  as 
well  as  in  concentrated  nitric  acid,  if,  as  I  must  once 
more  repeat,  the  circuit  is  closed  exactly  in  the  order 
I  have  described.  If  you  employ  an  acid  of  specific 
gravity  1*36  diluted  with  ten  times  its  volume  of 
water,  and  close  the  circuit,  for  example,  with  the 
negative  pole,  not  the  smallest  bubble  of  oxygen 
appears  on  the  iron  wire  forming  the  positive  pole  ; 
on  the  contrary  an  iron  salt  is  produced  which  sinks 
down  in  yellowish-brown  streams.  The  same  occurs 
even  in  acid  diluted  with  400  times  its  volume  of 
water.  But  if  the  end  of  the  iron  wire  which  has 
been  plunged  in  the  acid  is  held  only  for  a  few 
seconds  in  the  air,  and  then  the  circuit  is  closed  with 
it,  the  oxygen  again  appears  on  its  surface  in  the 
gaseous  form.  If  the  iron  terminal  from  which 


AND  SCHONBEIN  23 

oxygen  is  coining  off  is  made  to  touch  the  negative 
pole  within  the  liquid  for  a  few  moments,  the  oxygen 
no  longer  appears  on  its  surface  even  when  the  two 
wires  are  separated,  the  nitrate  being  produced  in- 
stead; but  in  this  case  also  the  iron  resumes  its 
former  indifference  to  the  oxygen  if  it  is  held  in  the 
air.  I  have  measured  the  quantities  of  the  gases 
developed  in  the  same  time  at  the  two  poles  and 
found  that  the  volume  of  the  oxygen  collected  at  the 
positive  iron  electrode  bears  to  that  of  the  hydrogen 
produced  at  the  negative  pole  the  ratio  1 : 2,  which 
may  serve  as  a  further  proof  that  under  these  condi- 
tions the  iron  is  not  in  the  least  oxidized.  Iron 
placed  under  the  same  conditions  in  water  to  which 
sulphuric  or  phosphoric  acid  has  been  added,  likewise 
develops  oxygen  gas ;  but  if  the  metal  has  previously 
been  placed  in  water  containing  sulphuric  acid,  or  if 
the  circuit  is  closed  with  the  negative  pole,  this 
phenomenon  does  not  occur.  If  the  pole  wires  from 
which  the  gases  are  coming  off  are  made  to  touch  for 
a  moment  within  the  liquid,  then,  after  they  are 
separated,  no  further  development  of  oxygen  takes 
place,  even  if  the  iron  wire  is  held  for  some  time  in 
the  air.  In  water  containing  potash,  the  oxygen 
always  appears  in  the  free  state  on  the  iron,  in  what- 
ever manner  the  circuit  is  closed.  It  is  hardly 
necessary  to  say  that  the  iron  must  be  the  positive 
pole.  In  order  to  bring  to  a  conclusion  a  letter 
which  is  already  too  long,  I  shall  stop  here  and  take 
the  liberty  of  drawing  your  attention  to  some  papers 
of  mine,  in  which  the  phenomena  I  have  described 


24  LETTERS  OF  BEEZELIUS 

are  treated  in  more  detail,  and  which  I  hope  will 
soon  appear  in  Poggendorff's  Annalen.  These  pheno- 
mena seem  to  me  to  be  of  the  more  importance  in 
that  they  do  not  agree  with  the  electro-chemical 
theory  which  is  at  present  accepted.  You  have 
already  thrown  light  on  so  many  of  the  dark  places 
of  chemistry  that  I  have  no  doubt  you  will  also  be 
able  to  give  a  satisfactory  solution  of  the  problem 
which  my  observations  present. 

Finally,  I  would  once  more  ask  you  to  pardon  the 
liberty  I  have  'taken ;  and  I  beg  to  subscribe  myself 
with  the  utmost  respect  and  esteem, 

Your  obedient  servant, 

Dr.  SCHONBEIN, 
Professor  of  Chemistry. 


Berzelius  answered  in  the  following  letter,  which  reached 
Bale  on  the  15th  of  May  1837  :— 


II 
Berzelius  to  Schonbein 

STOCKHOLM,  tth  May  1837. 

DEAR  SIR, 

There  is  an  old  proverb:  Quod  differtur, 
aufertur.  This  might  well  be  applied  to  my  answer 
to  the  letter  with  which  you  favoured  me  on  22nd 
April  1836,  and  in  which  you  communicated  to  me 
your  observations  on  the  peculiar  behaviour  of  iron 
in  the  presence  of  nitric  acid.  I  was  away  when  the 


AND  SCHONBEIK  25 

letter  arrived,  and  did  not  get  home  until  it  had 
been  awaiting  me  for  some  time,  so  I  repeatedly  put 
off  tendering  you  my  thanks.  The  preparation  of 
my  Jahresbericht  for  publication  reminded  me  of  it 
once  more,  and  so  I  now  express  to  you  my  sincere 
gratitude  for  the  interesting  information  it  contains. 
In  it  you  say  that  you  wish  me  to  give  you  my  views  on 
the  cause  of  these  remarkable  phenomena.  I  certainly 
agree  with  you 1  that  neither  Faraday 2  nor  Mousson 3 
has  suggested  an  acceptable  theory.  Indeed  it  would 
seem  hardly  possible  to  decide  what  explanation  is 
the  correct  one ;  but  I  maintain  that  a  very  likely 
interpretation  might  be  deduced  from  your  experi- 
ments, one  which  Faraday  in  fact  has  already 
suggested  in  his  last  communication  to  the  Editor  of 
the  Philosophical  Magazine]  I  mean  the  change  of 
electrical  condition  previously  observed  by  de  la 
Eive 4  and  Marianini,5  a  change  which,  at  any  rate  in 
metals,  can  be  maintained  for  some  time.  It  appears 
that  iron  possesses  a  power  as  peculiar  to  itself  as, 
for  example,  its  power  of  receiving  magnetic  polariza- 

1  Berzelius  is  here  referring  to  the  following  of  Schonbein's 
papers :  "  Bemerkungen  iiber  Faraday's  Hypothese  in  Betreff 
der  Ursache    der   Passivitat    des    Eisens    in    Salpetersaure." 
Poggend.  AnnaL,  vol.  xxxix.  (1836)  p.  137 ;  and  "  Die  Unzulang- 
lichkeit  der  bisherigen  Hypothesen  iiber  die  Passivitat  des 
Eisens,"  loc.  cit.,  p.  342,  which,  however,  was  printed  after 
Schonbein's  letter. 

2  Phil.  Mag.,  vol.  ix.  (1836)  pp.  57  and  122. 

3  Poggend.  Annal.,  vol.  xxxix.   (1836)  p.  330 ;  and  Bibl. 
Univ.,  vol.  v.  (1836)  p.  165. 

4  Bibl.  Univ.,  vol.  iii.  (1836)  p.  375  ;  and  Mrfmoires  de  la  Soc. 
de  Phys.  et  d'Histoire  Nat.  de  Geneve,  vol.  vii.  (1836)  p.  457. 

5  Annal.  de  Chimie  et  de  Physique,  vol.  xlv.  (1830)  p.  113. 


26  LETTEES  OF  BEEZELIUS 

tion,  of  passing  from  an  electro-positive  to  an  electro- 
negative state,  and  remaining  in  this  state  under 
suitable  conditions,  thus  changing  from  an  oxidizable 
to  a  noble  metal.  If  we  admit  this,  the  question 
arises,  What  are  the  means  by  which  this  new 
electrical  state  is  produced  ?  Your  experiments 
indicate  two  distinct  methods  by  which  it  can  be 
effected :  in  the  first  place  by  communicating  to  the 
iron  the  electrical  condition  of  some  other  body,  for 
example  platinum,  gold,  concentrated  nitric  acid, 
possibly  also  ferric  oxide,  and  in  the  next  place  by 
means  of  contact  electricity,  whereby  a  body  with  a 
strong  positive  charge,  such  as  the  positive  pole  of 
a  battery  or  a  solution  of  an  alkaline  hydrate,  pro- 
duces in  the  iron  a  charge  of  the  opposite  character. 
But  of  course  you  cannot  admit  the  latter  assumption, 
since  you  accept  de  la  Kive's  view  that  electricity  of 
an  opposite  character  cannot  be  produced  by  contact.1 
In  this,  however,  I  do  not  agree  with  you;  I  am 
firmly  convinced  that  when  we  understand  the  cause 
of  this  remarkable  property  of  iron  we  shall  find  in 
it  one  more  proof  that  Volta's  conception  was  more 
profound  and  nearer  the  truth  than  that  of  his 
opponents,  who,  by  admitting  that  electricity  and 
chemical  affinity  are  different  manifestations  of  the 
same  force,  acknowledge,  though  without  being  con- 
scious of  so  doing,  that  Volta  was  right. 

In  the  older  papers2  on  the  subject,  ammonia  also 

1  Cf.  Berzelius,  Jahresbericht.    Translated  by  "Wohler.    Vol. 
xvii.  (1838)  pp.  32  and  116. 

2  Keir,  Phil.   Trans.  (1790)   p.  359 ;    Wetzlar,   Schweigger 


AND  SCHONBEIN  27 

is  said  to  have  the  power  of  bringing  iron  into  this 
condition.  It  would  be  well  worth  while  investigating 
to  what  extent  the  other  two  magnetic  metals, 
nickel  and  cobalt,  have  this  property ;  even  if  they  do 
not  possess  it  to  the  same  degree,  they  may  show 
some  indications  of  its  existence.1 

I  hope  you  do  not  intend  to  abandon  this  work 
just  yet ;  it  is  conceivable  that  you  may  be  able  to 
discover  a  method  for  making  iron  in  any  quantity 
retain  this  condition  for  any  length  of  time :  such 
a  discovery  would  be  of  the  highest  value. 

I  have  the  honour  to  remain, 

With  the  profoundest  respect, 

Yours  obediently, 

JAG.  BERZELIUS. 

In  a  letter,  written  in  French,  of  the  12th  of  January 
1838,  Berzelius  as  permanent  secretary  of  the  Academy 
acknowledges  the  receipt  of  the  paper  entitled :  "  The 
behaviour  of  iron  towards  oxygen,"  2  and  to  the  printed 
form  adds  a  few  words  of  thanks  on  his  own  behalf  for 
the  copy  sent  to  him  personally. 

The  letter,  however,  contains  nothing  worth  reprinting. 

Jahrb.,  vol.  xix.  (1827)  p.  470  ;  vol.  xx.  (1827)  pp.  88  and  129  ; 
vol.  xxv.  (1829)  p.  206  ;  Fechner,  ibid.,  vol.  xxii.  (1828)  p.  27  ; 
vol.  xxiii.  (1828)  pp.  61,  129  and  429  ;  vol.  xxv.  (1829)  p.  223  ; 
Fischer,  Poggend.  AnnaL,  vol.  vi.  (1826)  p.  43  ;  Herschel,  ibid.j 
vol.  xxxii.  (1834)  p.  211 ;  cf.  also  Mousson,  ibid.,  vol.  xxxix. 
(1836)  p.  330. 

1  Cf.  Schonbein,  Phil.  Mag.,  vol.  xi.  (1837)  p.   544 ;    and 
Poggend.  Annal.,  vol.  xliii.  (1838)  p.  18. 

2  "  Das  Verhalten  des  Eisens  zum  Sauerstoff.    Ein  Beitrag  zur 
Erweiterung  electro-chemischer  Kenntnisse."    Von  Dr.  L.  [!]  F. 
Schonbein,  Professor  der  Chemie  in  Basel.     Basel,  1837. 


28  LETTEES  OF  BEEZELIUS 

On  October  14th  of  the  same  year,  Sehonbein  again 
writes  to  Berzelius  to  report  on  his  latest  electro-chemical 
investigations. 

Ill 
Sehonbein  to  Berzelius 

DEAR  SIR, 

I  trust  you  will  forgive  me  for  again  taking 
the  liberty  of  troubling  you  with  a  letter,  as  it  is  only 
scientific  motives  which  induce  me  to  write.  In  the 
last  few  months  I  have  spent  a  considerable  time 
on  voltaic  investigations,  and  have  arrived  at  some 
conclusions  which  seem  to  me  not  without  importance 
for  electro-chemistry,  and  which  I  think  you  will  be 
interested  to  hear. 

Becquerel  asserts  in  his  Traitt  that  wires  forming 
the  poles  of  a  circuit  possess  the  power  of  pro- 
ducing a  secondary  current  only  when  they  are  in  a 
saline  solution,  and  his  view  is  that  this  current  is 
due  to  the  re-combination,  under  suitable  circum- 
stances, of  the  base  and  the  acid  which  have  been 
separated  at  the  poles.  The  results  of  my  latest 
experiments  render  this  theory  untenable,  for  the 
following  reasons : — 

1.  Chemically  pure  hydrochloric   acid,   sulphuric 
acid,  potash  solution,  etc.,  when  used  to  complete  the 
circuit  admit   of  electrical  polarization   of  the  elec- 
trodes just  as  much  as  saline  solutions. 

2.  Polarization  of  the  electrodes  occurs  also  when 
the  battery  current  which  traverses  them  is  too  feeble 


AND  SCHONBEIN  29 

to  effect  electrolysis,  when,  for  example,  it  cannot 
decompose  potassium  iodide. 

There  is,  however,  another  fact  that  I  have  dis- 
covered, which  I  wish  particularly  to  recommend  to 
your  attention,  and  it  is  one  which  I  think  can 
hardly  fail  to  excite  the  interest  of  chemist  and 
physicist  alike.  It  is  the  capacity  which  every 
compound  liquid  conductor  (electrolyte)  possesses  of 
becoming  electrically  polarized. 

The  following  facts  will  serve  to  bear  out  my 
assertion.  Fill  a  U-shaped  tube  with  chemically 
pure  hydrochloric  acid;  put  a  platinum  wire  into 
each  limb,  and  connect  these  wires  for  a  few  seconds 
with  the  poles  of  a  battery  whose  current  is  too 
feeble  to  produce  on  the  electrodes  the  smallest  trace 
of  gas.  Now  remove  the  wires  from  the  tube,  and 
replace  them  by  another  pair  of  platinum  wires  which 
have  not  been  subjected  to  the  action  of  a  current ; 
finally,  connect  these  wires  with  a  galvanometer  of 
several  thousand  turns.  Under  these  circumstances 
the  needle  of  the  galvanometer  will  be  deflected  in 
such  a  direction  as  to  indicate  a  current  flowing  from 
the  limb  into  which  the  negative  electrode  dipped  to 
that  which  was  connected  with  the  positive  pole ;  in 
other  words,  the  former  limb  of  the  tube  behaves  as 
if  it  were  positive  to  the  latter.  This  fact  makes  it 
obvious  that  the  electrode  and  the  column  of  liquid 
directly  in  contact  with  it  are  both  electrically 
polarized  at  the  same  time  and  in  the  same  sense  by 
the  current  which  traverses  them.  As  my  work  on 
this  subject  will  soon  be  published  in  Poggendorff's 


30  LETTEES  OF  BEEZELIUS 

Annalen,1  I  will  not  enter  into  any  further  particulars 
here,  but  will  only  say  a  few  words  on  the  apparent 
cause  of  the  polarization  of  liquids. 

Since  neither  the  voltaic  nor  the  ordinary  chemical 
theory  of  galvanism  is  able  to  explain  this  strange 
phenomenon,  I  have  endeavoured  to  account  for  it 
in  the  following  manner.  A  current  which  is  too 
feeble  to  be  able  to  decompose  the  hydrochloric  acid 
through  which  it  passes  still  exerts  some  influence 
upon  it.  In  the  first  place  it  diminishes  the  mutual 
affinity  of  the  component  parts  of  each  molecule  of 
acid,  though  without  actually  separating  them ;  and 
in  the  second  place,  such  a  current  arranges  all  the 
acid  molecules  so  that  their  hydrogen  is  directed 
towards  the  negative  and  their  chlorine  towards  the 
positive  pole.  Now,  if  we  assume  further  that  in 
consequence  of  a  certain  inertia  of  the  atoms  this 
condition  of  the  acid  does  not  disappear  at  once  when 
the  current  is  interrupted,  but  that  the  constituent 
parts  of  each  molecule  return  only  by  degrees  to 
their  previous  condition  of  intimate  connection,  then 
this  act  of  re-combination  of  the  hydrogen  and  chlorine 
necessarily  must,  in  accordance  with  the  funda- 
mental laws  of  electro-chemistry,  produce  a  current 
of  exactly  the  kind  which  I  have  observed.  That  is 
to  say,  the  liquid  column  which  was  connected  with 
the  negative  pole  must  be  positive  to  that  which  was 
connected  with  the  positive  pole ;  and  this  condition 
of  electrical  polarization  must  continue  until  the 
original  equilibrium  between  the  hydrogen  and 
1  Poggend.  AnnaL,  vol.  xlvi.  (1839)  p.  109. 


AND  SCHONBEIN  31 

chlorine  atoms  has  been  restored  throughout  the 
whole  system  of  molecules.  Now  experiment  has 
shown  that  the  current  produced  by  the  polarized  acid 
does  as  a  fact  last  for  a  considerable  time,  as  you  will 
find  stated  in  the  paper  to  which  I  have  referred. 

If  my  hypothesis  ascribes  the  polarization  in 
question  to  its  true  cause,  it  must  lead  to  the  import- 
ant conclusion  for  theoretical  chemistry  that  between 
the  complete  separation  of  two  elements  and  their 
most  intimate  chemical  union  there  exist  intermediate 
conditions  of  combination,  of  which  as  yet  we  know 
nothing ;  unless  indeed  isomerism  points  to  some  such 
relation.  As  you  may  readily  conceive,  I  shall 
devote  my  whole  attention  to  a  subject  of  such  great 
theoretical  interest,  and  shall  endeavour  by  pursuing 
my  investigations  to  throw  still  more  light  on  the 
question.  If  it  were  not  too  much  presumption  on 
my  part  I  would  ask  you  to  be  so  kind  as  to  com- 
municate to  me  at  your  leisure  your  views  as  to  the 
cause  of  the  electrical  polarization  of  liquid  electro- 
lytes. To  a  student  of  chemistry  any  suggestion 
from  so  practised  a  master  would  be  a  cause  of 
gratification  and  encouragement. 

In  conclusion,  I  should  be  much  obliged  if  you 
would  tell  me  whether  the  Eoyal  Academy  of 
Stockholm  receives  papers  in  German,  and,  if  so, 
what  formalities  have  to  be  observed. 

I  have  the  honour  to  remain,  dear  Sir, 
Your  most  obedient  servant, 

C.  F.  SCHONBEIN. 

BALE,  Uth  October  1838. 


32  LETTEKS  OF  BEKZELIUS 

In  a  comparatively  short  time,  that  is  to  say  in  less 
than  a  month,  Schonbein  received  the  following  reply, 
which  reached  Bale  on  the  25th  of  November. 


IV 
Berzelius  to  Schonbein 

STOCKHOLM,  I3th  November  1838. 

DEAK  SIB, 

I    am    greatly   indebted    to    you    for    your 
interesting  communication  of  14th  October. 

The  polarization  observed  in  the  case  of  the  so- 
called  liquid  conductors  is  an  experimental  proof  of 
an  assumption  which,  in  my  opinion,  is  quite  essen- 
tial to  the  theory  of  the  electrical  battery.  I  am 
confident  that  it  may  be  taken  as  proved  beyond 
a  doubt  that  all  substances,  from  the  metals  to  the 
worst  conductors,  as  glass  and  resin,  are  capable  of 
assuming  electric  polarity,  which  will  have  a  greater 
tension  and  last  the  longer  the  greater  their 
resistance.  This  polarity  is  produced  by  every 
disturbance  of  electric  equilibrium,  but  the  less 
resistance  a  body  has,  the  more  rapidly  does  it  dis- 
appear, and  the  less  is  its  tension.  Hence  the  great 
difficulty  of  actually  exhibiting  it  in  the  case  of  good 
conductors.  But  it  is  precisely  this  property  of  a 
liquid  or  moist  conductor  on  which  the  phenomena 
of  a  hydro-electric  pile  depend,  whether  the  initial 
destruction  of  electrical  equilibrium  is  due  to  contact 
electricity  or  to  chemical  action  ;  and  without  it  the 


AND  SCHONBEIN  33 

increase  of  tension  in  the  poles  of  a  battery  when  the 
circuit  is  open  would  be  inexplicable :  for  this  tension, 
generally  speaking,  is  greater,  the  weaker  the  current 
when  the  circuit  is  closed  and  the  greater  the  resist- 
ance of  the  liquid.  Thirty-six  years  ago  I  put 
forward  as  an  experiment  a  theory  of  the  galvanic 
battery,  which,  however,  no  longer  has  much  claim 
to  attention ;  you  will  find  it  in  Gehlen's  Journal  for 
1803  or  1804.1  In  this  theory  I  developed  the  view 
that  the  state  of  polarization  of  a  liquid  conductor  is 
an  essential  condition  of  the  difference  of  potential  of 
an  electric  battery,  and  it  is  still  at  the  present  time 
my  firm  conviction  that  it  is  necessary  to  a  right 
understanding  of  hydro-electric  phenomena.  I  main- 
tain that  you  need  not  assume  any  special  state  of 
combination  in  the  liquid  to  explain  its  polarity,  any 

1  The  date  [1803  or  1804]  points  to:  "Afhandling  om 
Galvanismen,"  Stockholm,  1802 ;  however,  he  is  probably 
referring  to  :  "  Elektriska  Stapelns  Theori,"  Hisinger  Afhandl. 
i  Fysik,  vol.  ii.  (1802),  which  appeared  in  1807,  and  was  also 
printed  in  Gehlen's  Journal,  vol.  iii.  (1807)  p.  177.  In  the 
early  numbers  of  Gehlen's  Neues  allgemeines  Journal  der 
Chemie,  in  6  volumes  [1803-1806],  there  is  no  such  paper  by 
Berzelius  ;  on  the  other  hand,  there  are  some  other  papers,  the 
titles  of  which  I  will  give  here,  as  I  failed  to  find  them  in 
Poggendorff's  Handworterbuch  or  in  the  Catalogue  of  Scientific 
Papers  of  the  Royal  Society:  1.  "Yersuch  iiber  die  Farbung 
der  Thierknochen  durch  genossene  Farberrothe,"  vol.  iv.  (1804) 
p.  119.  2.  "Uber  die  Zusammensetzung  des  Menschenkothes," 
vol.  vi.  (1806)  p.  510.  3.  "  tlber  das  oxidierte  Stickgas,  die 
Thenard'sche  Fettsaure,  Flussspathsauregehalt  des  Zahn- 
schmelzes,"  loc.  cit.  p.  590.  Of  the  copy  of  Gehlen's  Neues 
allgemeines  Journal,  to  which  I  had  access,  the  6th  number  of 
the  4th  volume  was  missing.  I  am  therefore  unacquainted 
with  its  contents. 


34  LETTERS  OF  BEEZELIUS 

more  than  in  the  resinous  disk  of  the  electrophorus, 
which  can  receive  a  higher  charge  and  retain  it  for 
a  very  long  time ;  in  fact,  the  power  of  becoming 
polarized  must  be  a  fundamental  property  of  all 
bodies. 

I  have  read  with  the  greatest  interest  the  papers 
you  published  in  Poggendorff's  Annalen  and  in  the 
English  Journals,  and  can  only  urge  you  to  follow 
up  this  important  investigation. 

With  the  profoundest  respect, 
Dear  Sir, 

Yours  very  truly, 

JAC.  BERZELIUS. 


Schonbein  to  Berzelius 

DEAR  SIR, 

I  have  taken  the  liberty  of  sending  you  the 
last  number  of  the  Transactions  of  the  Swiss 
Association  for  the  Advancement  of  Science,  with 
a  humble  request  that  you  will  give  it  a  kindly 
reception. 

Though  it  does  not  contain  much  of  great  interest, 
you  will  perhaps  gather  from  it  that  the  Swiss 
have  at  least  the  wish  to  enlarge  the  boundary  of 
science. 

The  accompanying  three  numbers  of  the  Eeport  of 
the  work  of  the  Scientific  Club  of  this  town  are 
intended  for  the  Eoyal  Academy,  and  as  President  of 


AND  SCHONBEIN  35 

that  Club  I  request  you  to  be  so  good  as  to  forward 
them  to  their  destination. 

I  thank  you  most  sincerely  for  your  kindness  in 
answering  the  letter  in  which  I  had  the  honour  to 
inform  you  of  my  observations  on  the  polarization  of 
water  and  other  electrolytic  liquids.  In  the  course 
of  the  last  few  months  I  have  instituted  a  large 
number  of  new  experiments  on  this  subject,  and 
have  arrived  at  results  which  in  my  opinion  give 
a  satisfactory  explanation  of  the  phenomenon.  In 
a  paper  which  will,  I  hope,  soon  be  published  in 
Poggendorff's  Annalen,1  I  have  described  part  of  my 
observations  and  have  endeavoured  to  show  that 
electrolytic  liquids  are  not  capable  of  voltaic  polariza- 
tion in  the  proper  sense,  and  that  the  current  which 
is  produced  by  the  so-called  polarized  bodies  is  due 
to  chemical  action.  I  rely  chiefly  on  the  following 
facts  to  prove  the  correctness  of  this  view.  An 
aqueous  solution  of  hydrogen  (containing  some 
sulphuric  acid  to  make  it  a  better  conductor)  bears 
the  same  electrical  relation  to  an  aqueous  solution  of 
oxygen  (also  containing  sulphuric  acid),  that  the 
liquid  (water  acidified  with  sulphuric  acid)  in  one 
limb  of  a  U-tube,  in  which  the  negative  pole  of  a 
battery  has  been  placed  bears  to  the  same  liquid  in 
the  other  limb  connected  with  the  positive  pole. 
The  two  latter  liquids  only  show  themselves  polarized 
after  the  current  has  traversed  them,  if  they  are 
connected  with  the  circuit  by  means  of  platinum 
wires  and  not  if  wires  of  gold  or  silver  are  employed. 
1  Poggend.  AnnaL,  vol.  xlvii.  (1839)  p.  101. 


36  LETTEES  OF  BEEZELIUS 

This  is  exactly  the  behaviour  of  the  two  liquids  first 
mentioned,  a  solution  of  hydrogen  and  a  solution  of 
oxygen  or  of  ordinary  atmospheric  air.  If  the  water 
had  been  actually  polarized  by  the  current  from  the 
battery,  one  would  of  course  get  a  secondary  current 
whether  the  wires  used  to  close  the  circuit  were  of 
gold  or  platinum.  I  have  given  a  detailed  account 
of  this  subject  in  several  journals,1  which  you  will 
doubtless  soon  receive,  and  so  it  is  unnecessary  for 
me  to  enter  into  particulars  here;  but  I  cannot 
refrain  from  making  the  general  remark  that  my 
investigations  appear  to  show  that  the  act  of 
chemical  combination  of  the  elements  is  not  due  to 
the  play  of  electrical  forces,  or,  in  other  words,  that 
affinity  and  electricity  are  not  the  same  thing, 
though  they  are  mutually  dependent.  I  am  intend- 
ing soon  to  develop  these  views  of  mine  in  a  separate 
treatise,  and  to  establish  their  truth  on  experimental 
grounds. 

If  I  venture  to  express  a  doubt  as  to  the  truth  of 
the  electro-chemical  theory,  it  is  in  the  conviction 
that  its  founder  would  be  the  last  man  to  blame  me 
for  so  doing,  and  I  am  sure  that  you  will  weigh  the 
arguments  which  I  have  to  bring  against  it  in  a 
spirit  of  the  most  perfect  impartiality.  You  are  too 
much  inspired  by  a  pure  love  of  science,  and  you 
take  too  high  a  position  in  the  scientific  world,  for 
subordinate  considerations  to  exercise  any  influence 
on  your  judgment.2 

1  Journal  fur  prakt.  Chemie,  vol.  xx.  (1840)  p.  129  [?]. 

2  Cf.  Poggend.  Annal.,  vol.  xlvi.  (1839)  p.  336. 


AND  SCHONBEIN  37 

I  trust  you  will  pardon   my  writing   to  you  so 
often,  and  with  the  greatest  respect 
I  have  the  honour  to  be, 

Dear  Sir, 
Your  most  obedient  servant, 

C.  F.  SCHONBEIN. 


BALE,  28ta  March  1839. 

Berzelius  replied  somewhat  briefly  to  this  letter.  If,  in 
fact,  though  I  am  not  quite  certain  about  it,  the  passage 
in  Schbnbein's  letter  refers  to  his  brief  summary  in  vol. 
xx.  of  the  Journal  fur  praktische  Chemie,  which  how- 
ever was  not  printed  till  1840,  he  rejects  Schonbein's 
interpretation  with  the  following  curt  and  severe  comment  : 
"Even  these  outlines  show  that  Schonbein  has  not 
grasped  the  spirit  of  the  electro-chemical  theory."  1  I 
imagine  that  the  following  letter  of  Berzelius  relates  to 
this  paper  of  Schonbein's,  because  in  the  Jahresbericht, 
vol.  xxi.,  it  is  discussed  simultaneously  with  the  paper  of 
Faraday's  mentioned  below. 


VI 
Berzelius  to  Schonbein 

STOCKHOLM,  18th  September  1840 

The  permanent  secretary  of  the  Academy  to 
Professor  Schonbein,  Bale. 

The  Academy  has  received  your  three  treatises, 
entitled,  "Bericht  iiber  die  Verhandlungen  der 

1  Jahreslericht,  vol.  xxi.  (1842)  p.  33. 


38  LETTERS  OF  BERZELIUS 

Naturf orschenden  Gesellschaf t  in  Basel,"  also, "  Mittel 
und  Hauptresultate  aus  meteorologischen  Beobacht- 
ungen  in  Basel,"  by  Peter  Merian,  which  you  were 
kind  enough  to  send  to  it.  I  am  instructed  to 
express  to  you  their  gratitude.  The  papers  have 
been  deposited  in  the  library  of  the  Academy.  With 
the  assurance  of  my  utmost  regard, 

I  have  the  honour,  Sir,  to  remain, 

Your  very  humble  servant, 

JAC.  BEEZELIUS. 

P.S. — I  must  thank  you  on  my  own  behalf  for  the 
number  of  the  Transactions  of  the  Swiss  Association 
for  the  Advancement  of  Science  of  their  meeting  at 
Bale  in  1838,  which  you  were  kind  enough  to  send 
me,  and  also  for  the  very  friendly  letter,  in  which 
you  stated  the  reasons  which  induced  you  to  ascribe 
hydroelectric  phenomena  to  the  play  of  chemical 
affinities.  This  is  also  the  opinion  which  Mr.  Faraday 
arrived  at  after  his  long  series  of  researches  on  the 
subject1;  and  it  certainly  is  the  opinion  which 
suggests  itself  at  first  sight.  I  dare  say  you  are 
aware  that  I  do  not  adhere  to  it,  and  I  am  always 
waiting  for  some  of  the  physicists  who  hold  the  so- 
called  chemical  theory  to  explain  by  this  hypothesis 
in  a  satisfactory  manner  the  chemical  phenomena 
brought  about  by  the  electric  current,  as  for  example 
the  reduction  of  potash ;  for  a  theory  which  fails 
to  give  any  distinct  or  logical  explanation  of  the 
chemical  decompositions  produced  by  the  electrical 

1  Phil.  Mag.,  i.  16  (1840)  p.  336. 


AND  SCHONBEIN  39 

current  cannot  be  the  true  theory  of  the  electric 
battery  or  of  the  cause  which  renders  it  active.  On 
the  other  hand  the  contact  theory,  according  to  which 
chemical  affinities  depend  on  the  electrical  state  and 
not  vice  versa,  adequately  explain  the  chemical 
phenomena  which  the  battery  produces. 


VII 
Schbnbein  to  Berzelius 

DEAR  SIR, 

I  take  the  liberty  of  sending  you,  by  favour 
of  Herr  Schiitz  of  Summiswald,  a  paper 1  which  you 
have  probably  not  yet  seen,  and  whose  contents  will, 
I  think,  not  be  wholly  without  interest  to  you. 
Unfortunately,  the  accumulation  of  business  has 
prevented  me  from  following  up  further  the  subject 
which  is  there  discussed ;  and  I  have  not  had  time 
to  prepare  the  odoriferous  principle  (which  I  may 
mention  that  I  have  called  ozone)  in  sufficiently 
large  quantities  to  be  able  to  determine  its  chemical 
properties  accurately.  As  soon  as  I  have  the  necessary 
leisure  I  shall  proceed  at  once  to  continue  this 
work,  and  shall  in  due  time  make  the  scientific 

1  The  reference  is  probably  to  the  paper:  "  Beobachtungen  liber 
den  bei  der  Electrolysation  des  Wassers  und  dem  Ausstromen 
der  gewohnlichen  Elektricitat  aus  Spitzen  sich  entwickelnden 
Geruch."  Which  edition  is  meant,  whether  AWiandl.  der 
Milnchner  AJcademie,  iii.  257,  or  Poggendorff,  50,  616, 1  cannot 
say.  In  the  Jahresbericht,  xxi.  (1842)  p.  39,  Berzelius  refers  to 
the  Annalen. 


40  LETTEES  OF  BEKZELIUS 

public  acquainted  with  the  results  of  my  investiga- 
tions. 

Meanwhile  I  have  practically  proved  that  ozone 
plays  an  important  part  in  the  so-called  voltaic 
polarization  of  water,  and  that  it  is  the  cause,  for 
example,  of  the  negativity  of  that  portion  of  the 
acidified  water  in  which  the  positive  pole  of  a  battery 
has  been  placed. 

I  should  be  excessively  obliged  if  you  would  take 
an  opportunity  of  letting  me  know  what  you  think 
of  the  conclusions  which  I  have  drawn  from  my 
experiments. 

Is  it  not  possible  that  we  might  sometime  have 
the  honour  and  pleasure  of  welcoming  you  in 
Switzerland?  I  do  not  think  you  would  find  our 
country  otherwise  than  agreeable.  I  have  for  a 
long  time  had  a  great  desire  to  see  your  interesting 
country,  but 1  having  got  a  wife  and  nearly  half  a 
dozen  of  children  I  am  nailed  down  to  a  spot  and 
cannot  think  of  moving  much  about. 

With  the  greatest  respect,  I  have  the  honour  to  be, 

Dear  Sir, 
Your  most  obedient  servant, 

C.  F.  SCHONBEIN. 

BALE,  llth  September  1840. 

I  do  not  possess  the  original  of  Berzelius'  answer  to  this 
letter,  in  which  Schonbein  gave  the  first  information  of  the 
discovery  of  ozone,  but  only  a  copy  (expressly  described 
as  such)  in  Schb'nbein's  own  hand.  In  April  "1840 

1  [The  rest  of  this  sentence  is  in  English  in  the  original.— Tr.] 


AND  SCHONBEIN  41 

Schonbein  had  sent  his  first  paper  :  "  Uber  die  materielle 
Ursache  der  Geruchsempfindung  bei  Elektricitats-Ent- 
wickelung  "  in  manuscript  with  a  letter  to  Schelling 1  at 
Munich.  In  his  answer  on  the  24th  of  April  of  the 
same  year  Schelling  speaks  in  the  highest  terms  of  the 
research,  which  he  had  immediately  passed  round  among 
the  members  of  the  mathematical  and  physical  class  of  the 
Royal  Academy ;  and  particularly  requests  Schonbein  to 
allow  them  to  print  it  in  their  Transactions,  "  to  which  it 
would  certainly  do  credit."  He  continues  as  follows : 
"  Steinheil 2  dabbles  in  many  things  without  obtaining  any 
results  ;  he  receives  £80  a  year  for  prosecuting  researches 
which,  however,  invariably  break  down  without  leading 
to  any  conclusions.  In  the  person  of  our  Crown  Prince  3 
we  possess  a  distinguished  patron  of  research,  especially 
on  scientific  lines.  Should  you  ever  be  unable  from  want 
of  pecuniary  resources  to  begin  a  lengthy  research,  from 
which  you  have  grounds  for  expecting  good  results,  let  me 
know  and  it  will  give  me  great  pleasure  to  awaken  the 
interest  of  our  generous  prince  on  your  behalf." 

Schonbein  consequently  sent  in  an  application  to  the 
Prince  through  Schelling  for  a  sum  of  money  to  purchase 
a  battery  ;  but  as  this  appeal  coincided  with  the  former's 
departure  for  Greece,  the  matter  could  not  then  be 
arranged.  Schelling  writes  on  the  21st  of  December 
1840  :  "I  am  sure  the  Prince  will  not  allow  the  matter  to 

1  Friedrich  Wilhelm  Joseph  Schelling,  born  in  1775  at  Leon- 
berg  in  Wurtemberg,  was  professor  at  Jena  in  1798,  at  Wiirz- 
burg  in  1803,  member  of  the  Munich  Academy  from  1806  to 
1820,  then  at  Erlangen  ;  in  1827  he  was  professor  at  Munich,  in 
1840  at  Berlin,  and  he  died  in  1854  at  Ragaz. 

2  Karl  August  Steinheil  was  born  in  1801  at  Rappoltsweiler 
in  Alsace,  and  died  in  1870  at  Munich.     From  1832  to  1849  he 
was  professor  of  physics  and  mathematics,  from  1835  an  ordin- 
ary member  of  the  Academy  at  Munich. 

3  Subsequently  King  Maximilian  II. 


42  LETTEES  OF  BEKZELIUS 

drop,  and  I  also  shall  not  fail,  whenever  I  have  a  con- 
venient opportunity,  to  remind  him  of  it.  I  regret  to 
say,  however,  that  the  Prince  has  taken  all  the  documents 
and  also  your  note  to  Berzelius  along  with  him." 

Schonbein  had  in  fact  enclosed,  as  a  recommendation, 
Berzelius'  letter  to  him  on  the  discovery  of  ozone.  Prince 
Maximilian  never  returned  it,  but  Schonbein  had  prudently 
retained  a  copy. 

VIII 
Berzelius  to  Schonbein  1 

STOCKHOLM,  3rd  November  1840. 

DEAK  SIR, 

I  thank  you  sincerely  for  your  paper  on  ozone, 
and  the  courteous  letter  which  accompanied  it.  I 
read  it  with  great  interest,  and  consider  it  highly 
probable,  as  you  suggest,  that  natural  waters  con- 
tain, though  in  very  minute  quantities,  some  volatile 
matter,  composed  possibly  of  hydrogen  and  ozone. 
The  building  up  of  this  body  in  some  conclusive 
manner  would  be  one  of  the  most  brilliant  chemical 
discoveries  ever  achieved  by  science.  I  need  hardly 
urge  you  not  to  let  the  matter  drop  before  you  are 
successful,  however  great  an  exertion  be  required.  It 
is  quite  probable  that  water  is  always  accompanied 
by  this  compound  in  nature,  for  we  know  that  common 
salt  never  occurs  in  nature  without  traces  of  sodium 
iodide  or  sodium  bromide. 

1  This  letter  is  mentioned  in  Hagenbach's  obituary  notice  of 
Schonbein.  [Basel  Universitats-Programm,  1868.] 


AND  SCHONBEIN  43 

In  former  times  I  noticed  that  whenever  I  per- 
formed electrical  experiments  for  some  time  continu- 
ously, for  which  purpose  I  employed  a  very  powerful 
battery,  the  whole  atmosphere  of  my  room  smelt  of 
phosphorus  for  hours  afterwards.  I  was  convinced 
that  this  could  not  result  from  the  action  of  electricity 
on  the  organs  of  smell,  since  it  continued  even  after 
the  disengagement  of  electricity  had  ceased ;  but  it 
seemed  impossible  to  determine  how  it  originated. 
I  hope  you  will  let  me  know  what  results  you  obtain 
by  continuing  these  experiments. 

With  the  greatest  respect, 

Yours  most  obediently, 

JAC.  BEEZELIUS. 


IX 
Schonbein  to  Berzelius 

MY  DEAR  BARON, 

I  take  the  liberty  of  sending  you  a  little 
work1  that  has  just  appeared,  in  which  I  have  dis- 
cussed some  physico-chemical  questions.  As  you 
will  see  from  its  contents,  the  views  which  I  have 
developed  as  to  the  relation  between  voltaism  and 
chemism  differ  in  important  respects  from  those  of 

1  He  refers  to  the  book  dated  December  1843,  and  dedicated 
to  A.  de  la  Rive,  entitled,  Beitrage  zur  Pliysikalisclien  Chemie, 
Basel,  1844.  It  is  divided  into  three  parts :  (1)  On  the  fre- 
quency of  contact- action  in  chemistry.  (2)  On  the  cause  of 
increase  of  conductivity  of  water  by  means  of  acids,  alkalis  and 
salts.  (3)  On  the  action  of  hydro-electric  currents. 


44  LETTEES  OF  BEEZELIUS 

Faraday  and  de  la  Eive ;  but  I  hope  that  this  will 
not  prevent  my  work  from  contributing  something 
towards  the  agreement  of  physicists  on  a  question 
which  has  so  long  been  the  subject  of  controversy. 
In  the  second  part  of  the  book  I  have  given  some 
conjectures  as  to  the  chemical  constitution  of  the  so- 
called  hydrated  acids  and  bases,  as  well  as  of  many 
double  salts.  I  am  really  very  curious  to  hear  what 
you  think  of  the  hypotheses  which  I  have  pro- 
pounded, and  you  would  be  doing  me  the  greatest 
kindness  if  you  would  take  an  opportunity  of  letting 
me  know  in  a  letter  what  is  your  frank  opinion  of 
them,  and  also  of  the  contents  of  the  first  section, 
dealing  with  contact  action.  I  have  been  much 
interested  to  learn,  from  a  communication l  of  yours 
to  the  Stockholm  Academy,  that  you  are  inclined  to 
ascribe  the  passivity  of  iron  to  an  allotropic  condi- 
tion of  the  metal.  The  only  remarkable  thing  about 
it  is  that  the  allotropy  should  be  confined  to  the 
surface,  and  not  extend  in  any  degree  to  the  interior 
of  the  iron;  for  the  current  which  determines  the 
passivity  of  the  surface  goes  through  every  part  of 
the  iron,  which  serves  as  positive  electrode.  The 
statements  which  Martens  of  Brussels  has  quite 
recently  made  to  the  Academy  of  that  town,2  accord- 
ing to  which  a  red  heat,  irrespective  of  any  oxidation, 
is  sufficient  to  secure  the  passivity  of  iron,  are  quite 

1  Stockholm  Acad.  Handl.  (1843)  p.  1  ;  and  Poggend.  Annal., 
vol.  Ixi.  (1844)  p.  14. 

2  Bruxelles  Acad.  Sci.  Bui  (1843)  [Pt.  2]  p.  406  ;  [Supple- 
ment in  Poggend.  AnnaL,  vol.  Ixi.  (1844)  p.  121]. 


AND  SCHONBEIN  45 

without  foundation,  as  I  have  convinced  myself  by 
repeated  experiments. 

With  the  greatest  respect  and  esteem, 

I  have  the  honour  to  be,  my  dear  Baron, 
Yours  most  sincerely, 

C.  F.  SCHONBEIN. 

BALE,  23rd  February  1844. 

Berzelius  made  no  answer  to  this  letter  of  Schonbein's, 
nor  does  the  Jaliresberwlit  contain  any  references  to  these 
questions  or  to  the  book  on  physical  chemistry  forwarded 
to  Berzelius. 

X 
Schonbein  to  Berzelius 

BALE,  \±th  April  1844. 

MY  DEAR  BARON, 

You  were  formerly  interested  in  my  experi- 
ments on  the  nature  of  the  electrical  odour,  and  so  I 
natter  myself  that  the  results  of  my  latest  work l  on 
this  subject  will  not  be  wholly  indifferent  to  you,  more 
especially  as  they  seemed  to  you  to  have  opened  a 
new  field  for  chemical  investigation.  You  will  re- 
member, no  doubt,  that  I  endeavoured  to  prove  the 

1  Lectures  delivered  at  meetings  of  the  Association  for  the 
Advancement  of  Science  at  Bale  on  the  3rd  and  17th  of  April 
and  the  15th  of  May  1844  :  Easier  Berichte,  vol.  vi.  (1844)  p.  16. 
Bibl.  Univ.,  vol.  1.  (1844)  p.  395  ;  collected  in  "  tjber  die 
Erzeugung  des  Ozons  auf  chemiscliem  Wege,"  Basel,  1844.  Pre- 
face dated  13th  May  1844. 


46  LETTEES  OF  BEKZELIUS 

chemical  identity  of  the  substance  produced  by  the 
electrical  discharge  in  the  air  and  that  formed  in  the 
electrolysis  of  water  from  the  similarity  of  their 
voltaic  properties ;  and  that  the  electric  character  of 
my  ozone  together  with  its  chemical  behaviour  led 
me  to  conjecture  that  it  was  a  body  very  similar  to 
chlorine.  Quite  recently  I  have  succeeded  (at  least 
I  think  I  have)  not  only  in  showing  by  a  satisfactory 
proof  that  the  two  odoriferous  principles  are  identical, 
but  also  in  preparing  the  substance  by  a  chemical 
method,  and  that  in  such  quantities  that  I  have 
every  reason  to  hope  that  I  shall  be  able  to  isolate  it. 
The  identity  and  the  haloid  character  of  the  body 
produced  under  such  different  conditions  are  shown  : 
1.  By  the  complete  similarity  of  the  smell  of  chemical, 
voltaic  and  electrical  ozone.  2.  By  the  remarkably 
strong  negative  polarization  produced  by  these  three 
substances.  3.  By  the  destruction  of  its  smell  and  of 
its  polarity  by  all  bodies  which  take  up  or  combine 
chemically  with  chlorine ;  for  example,  easily  oxidized 
metals,  stannous  chloride,  ferrous  chloride,  ferrous 
sulphate,  alkaline  solutions,  etc.  4.  By  its  power  of 
destroying  vegetable  colours  with  great  energy.  5. 
By  its  power  of  instantly  decomposing  potassium 
iodide  and  setting  iodine  free ;  of  turning  potassium 
ferrocyanide  into  ferricyanide ;  of  breaking  up 
hydrogen  sulphide,  hydrogen  selenide,  etc. ;  of  con- 
verting sulphurous  into  sulphuric  acid  in  the  presence 
of  water,  thus  decomposing  water  under  exactly  the 
same  conditions  as  chlorine ;  and  of  being  destroyed 
by  ammonia.  I  might  mention  yet  more  chemical 


AND  SCHONBEIN  47 

facts  which  all  go  to  establish,  in  the  most  satisfactory 
manner,  the  analogy  between  chlorine  and  my 
ozone. 

I  have  no  doubt  that  you  will  be  astonished  when 
I  tell  you  how  ozone  can  be  produced  chemically,  for 
the  conditions  of  its  formation  are  such  as  would  not 
lead  one  to  expect  in  the  remotest  degree  the  results 
which  are  actually  obtained.  The  method  is  this: 
Commercial  phosphorus  is  allowed  to  stand  in  a  flask 
filled  with  atmospheric  air.  If  the  temperature  of  the 
experiment  is  only  a  few  degrees  above  zero,  the  air 
above  the  phosphorus  somewhat  rapidly  assumes  a 
positive  potential,  that  is,  it  has  the  power  of  polar- 
izing positively  a  strip  of  gold-leaf  held  in  it.  If  the 
temperature  is  not  raised  in  any  way  the  air  remains 
in  this  voltaic  condition  and  smells  of  phosphorus, 
i.e.,  like  garlic.  But  if  the  air  is  warmed  to  8-12° 
its  positive  potential  changes  rapidly  to  the  opposite ; 
that  is,  it  assumes  the  power  of  polarizing  a  gold-leaf 
negatively.  This  change  of  the  electrical  condition  is 
accompanied  by  an  alteration  of  smell.  The  air  now 
smells  just  like  electricity  discharging  itself  from  a 
point,  or  like  the  oxygen  which  is  set  free,  for 
example,  on  the  positive  pole  in  the  electrolysis  of 
acidified  water.  The  higher  the  temperature  the 
more  rapid  is  the  change  which  I  have  described; 
and  if  the  phosphorus  is  heated  almost  to  its  melting- 
point,  the  alteration  of  smell  and  of  voltaic  condition 
occurs  in  the  course  of  a  few  minutes,  or  even  in  a 
much  shorter  time ;  while  at  the  ordinary  tempera- 
ture several  hours  are  required.  When  once  the 


48  LETTEES  OF  BEBZELIUS 

negative  polarization  or  the  electrical  smell  has 
become  perceptibly  strong,  a  moist  or  air-dried  strip 
of  litmus  paper  plunged  in  the  air  is  fairly  rapidly 
bleached  and  tincture  of  litmus  or  indigo  solution  is 
decolorized,  exactly  as  it  is  by  chlorine.  If  such  air 
is  shaken  with  potassium  ferrocyanide  solution  the 
liquid  becomes  intensely  yellow,  and  when  treated 
with  pure  ferrous  sulphate  gives  a  blue  precipitate. 
Potassium  iodide  solution  shaken  with  it  is  turned 
yellow,  and  moist  starch  paste  mixed  with  this  salt 
instantly  becomes  blue. 

I  may  mention  here  that  strips  of  paper  soaked  in 
starch  solution  containing  potassium  iodide  form  the 
most  convenient  and  the  most  delicate  test  for  ozone  ; 
they  indicate  its  presence  even  when  a  very  sensitive 
galvanometer  fails  to  do  so,  or  when  the  smell  cannot 
be  perceived. 

Just  one  example  to  prove  the  truth  of  this  state- 
ment. A  small  piece  of  phosphorus  still  covered 
with  moisture  will  not  turn  blue  a  piece  of  test 
paper  held  above  it,  but  if  the  phosphorus  is  rubbed 
with  blotting  paper,  with  gentle  friction,  the  paper 
becomes  decidedly  blue  in  the  course  of  a  few  seconds. 
It  is  a  remarkable  fact  that  very  small  quantities  of 
ether  or  alcohol  vapour,  olefiant  gas,  as  well  as  some 
other  vapours  and  gases,  such  as  sulphurous  acid, 
hydrogen  sulphide,  etc.,  entirely  prevent  the  forma- 
tion of  ozone  in  atmospheric  air ;  and  this  is  the 
action  generally  of  all  substances  which  arrest  the 
luminescence  or  slow  combustion  of  phosphorus  in 
the  air.  I  must  here  mention  that  in  pure  oxygen 


AND  SCHONBELNT  49 

no  ozone  is  produced  at  temperatures  at  which  in 
atmospheric  air  it  is  formed  in  comparatively  large 
quantities.  I  need  scarcely  say  that  in  hydrogen, 
carbonic  acid,  ethylene,  hydrogen  sulphide,  etc.,  no 
ozone  is  formed ;  but  I  should  perhaps  add  that  the 
same  is  the  case  in  nitrous  oxide.  It  is  further  a 
strange  fact  that  the  luminescence  of  phosphorus 
stands  in  the  closest  possible  connection  with  the 
production  of  ozone  and  with  the  presence  of  nitrogen  ; 
but  the  limits  of  my  space  prevent  me  from  going 
further  into  this  question,  and  therefore  I  take  the 
liberty  of  referring  you  to  a  memoir1  which  will 
shortly  appear  in  print,  in  which  I  have  described 
the  results  of  my  experiments  in  detail.  As  already 
stated,  the  ozone  which  is  obtained  by  the  electrolysis 
of  water  has  every  one  of  the  properties  of  that  which 
I  have  prepared  from  phosphorus  and  atmospheric  air, 
so  that  not  the  slightest  doubt  remains  as  to  the 
identity  of  the  two  bodies.  But  that  the  strongly 
smelling  substance,  produced  by  the  discharge  of 
ordinary  electricity,  should  be  identical  with  chemical 
and  voltaic  ozone  is  a  fact  which  is  as  singular  as  it 
is  now  (in  my  opinion,  at  least)  unquestionable.  The 
experimental  proofs  of  the  correctness  of  my  assertion 
are  as  follows:  1.  The  bleaching  power  of  the  sub- 
stance produced  by  the  electric  discharge.  The 
accompanying  strip  of  paper  marked  No.  1  2  has  been 

1  The  book  mentioned  above,  on  the  chemical  preparation  of 
ozone. 

2  This  and  the  other  strips  are  still  attached  to  the  letter,  and 
show  clearly  the  similarity  of  the  bleaching  action. 


50  LETTEES  OF  BEKZELIUS 

bleached  by  electricity  in  the  following  manner. 
The  strip,  in  a  moist  condition,  was  placed  on  a 
platinum  plate  which  was  in  metallic  contact  with 
the  earth.  A  brass  wire  was  fixed  to  the  conductor 
of  the  electrical  machine  so  that  its  free  end  reached 
to  within  a  third  of  an  inch  of  the  strip.  When  the 
electrical  machine  was  set  in  motion,  part  of  the  strip 
was  thus  in  the  electrical  brush,  that  is,  in  the  place 
where  the  electric  smell  was  most  distinctly  perceptible. 
After  the  machine  had  been  worked  continuously  for 
four  hours  the  strip  appeared  bleached  as  you  see  it. 
(You  will  perhaps  be  interested  to  learn  that  the 
strip  which  I  am  sending  you  is  the  very  one  with 
which  I  for  the  first  time  proved  the  bleaching  power 
of  the  electrical  odour,  and  that  this  first  experiment 
was  performed  on  the  7th  of  April  1844.)  2.  The 
power  possessed  by  the  odoriferous  electrical  material 
of  converting  potassium  f  errocyanide  into  f erricyanide. 
A  drop  of  ferrocyanide  solution  brought  under  the 
above  conditions  assumes  even  after  a  few  minutes 
a  deep  yellow  colour,  and  then  on  treatment  with 
pure  ferrous  chloride  or  sulphate  gives  a  decided 
blue  precipitate.  After  a  thousand  turns  of  my 
machine,  a  drop  of  such  a  solution  gives  a  dark 
blue  precipitate.  3.  The  power  possessed  by  the 
electrical  odour  of  almost  instantly  turning  starch 
paste  containing  potassium  iodide  blue.  This  power 
has  indeed  long  been  known,  but  it  has  been  errone- 
ously interpreted ;  for  the  separation  of  iodine  does 
not  depend  on  the  electrical  decomposition  of  the 
haloid  salt,  nor  essentially  on  the  formation  of  nitric 


AND  SCHONBEIN  51 

acid,  as  Faraday  supposes.  It  is  to  the  production 
of  ozone  by  the  electricity  that  this  action  must  be 
ascribed.  4.  The  property  of  the  electrical  odour  of 
being  destroyed  by  sulphurous  acid,  hydrogen  sulphide 
and  hydrogen  selenide.  If  in  the  neighbourhood  of  a 
point  from  which  electricity  is  being  discharged  the 
merest  trace  of  sulphurous  acid  is  developed,  as  for 
example  by  burning  the  sulphur  of  an  ordinary  match, 
the  peculiar  smell  which  accompanies  the  discharge 
of  electricity  into  the  air  is  perceived  no  longer. 
Furthermore  the  electrical  brush  is  no  longer  able 
under  these  conditions  to  communicate  negative 
polarity  to  a  gold  or  platinum  strip  held  in  it,  or  to 
turn  potassium  iodide  starch  paste  blue.  Moreover 
if  such  a  strip  is  held  only  for  a  moment  in  a  flask 
containing  some  sulphurous  acid,  it  will  not  be  turned 
blue  when  exposed  to  the  action  of  the  electric  brush. 
The  action  of  hydrogen  sulphide  and  selenide  is 
similar  to  that  of  sulphurous  acid;  the  presence  of 
the  smallest  quantities  of  these  substances  in  the 
room  containing  the  electrical  machine  is  sufficient 
to  prevent  the  production  of  the  electrical  odour  at 
the  point  of  the  conductor  and  all  the  reactions  de- 
pending upon  it.  Now  these  substances  destroy 
chemically  or  voltaically  prepared  ozone  in  exactly 
the  same  manner  as  the  electrical  odour.  Hardly 
any  doubt  can  remain  as  to  the  identity  of  the  ozone 
prepared  in  the  three  ways  described,  and  it  may  be 
taken  as  incontestable  that  during  the  discharge  of 
electricity  into  the  air  a  haloid  substance  similar  to 
chlorine  is  formed.  Now  since  lightning  is  nothing 


52  LETTEES  OF  BEEZELIUS 

but  the  restoration  of  electrical  equilibrium  on  a 
large  scale,  it  seems  to  me  to  be  certain  that  the 
smell  or  pungent  vapour  observed  after  a  flash  of 
lightning  is  nothing  but  my  ozone.  At  any  rate  it 
must  form  an  important  constituent  of  the  odor- 
iferous body  which  is  so  produced.  My  investigations 
have  shown  that  ozone  is  not  produced  either  in  pure 
oxygen  or  carbonic  acid  under  conditions  of  tempera- 
ture in  which  it  is  produced  quite  easily  in  atmos- 
pheric air ;  and  I  have  also  found  that  in  air  which 
is'  completely  dried  with  calcium  chloride,  my  test 
paper  is  coloured  perceptibly  blue,  after  this  an- 
hydrous air  has  been  allowed  to  stand  for  some  time 
with  phosphorus.  Now  this  experiment  seems  to 
show  that  water  also  contributes  nothing  to  the 
formation  of  ozone.1  But  if  so,  there  is  no  known 
constituent  of  the  atmosphere  left  from  which  the 
ozone  could  possibly  originate,  except  nitrogen. 
Though  it  is  a  very  remarkable  fact  that  ozone 
should  be  produced  by  the  electrolysis  of  water,  and 
also  by  the  discharge  of  electricity  in  the  air,  yet  it 
is  still  more  extraordinary  that  so  eminently  electro- 
negative a  body  as  this  can  be  formed  in  the  presence 
of  phosphorus  and  even  by  its  means.  Indeed  if  a 
small  piece  of  phosphorus  is  placed  in  a  flask  contain- 
ing ozonized  oxygen  collected  at  the  positive  pole  of 
a  battery,  the  ozone  smell,  the  bleaching  power,  the 

1  This  remark  is  particularly  interesting,  because  it  is  dia- 
metrically opposed  to  his  later  view,  which  prevented  him  for 
such  a  long  time  from  accepting  Marignac's  explanation  of  the 
nature  of  ozone,  and  de  la  Hive's  proof  that  ozone  can  be 
formed  in  the  absence  of  water. 


AND  SCHONBEm  53 

negative  polarity,  and,  in  fact,  all  the  properties  of 
ozone  already  specified  disappear.  If  you  take  a 
piece  of  phosphorus  which  would  not  shine  in  the 
dark  or  colour  a  piece  of  my  test  paper  placed  near 
it,  and  hold  it  near  a  point  from  which  electricity  is 
being  discharged,  no  ozone  is  developed  at  the  point, 
starch  paste  containing  potassium  iodide  is  not  turned 
blue,  and  generally  none  of  the  phenomena  which  I 
have  described  as  accompanying  the  electrical  brush 
are  observed.  Are  we  then  to  suppose  that  voltaic 
and  electric  ozone  are  different  from  that  which  is 
prepared  from  atmospheric  air  by  means  of  phos- 
phorus, and  that  chemical  ozone  cannot  combine  with 
phosphorus  ? 

As  a  fact  there  is  no  such  difference,  as  the  follow- 
ing experiment  shows.  If  a  few  drops  of  ether  are 
allowed  to  fall  into  a  flask  filled  with  chemical  ozone, 
and  then  a  small  piece  of  phosphorus  added,  the  ozone 
smell  rapidly  disappears,  and  the  test  paper  is  no 
longer  turned  blue  by  the  air  in  the  flask.  The  ozone 
already  present  in  a  flask  containing  air  and  phos- 
phorus is  always  destroyed,  if  by  any  of  the  means 
which  I  have  described,  or  in  any  other  way,  the 
luminescence  of  the  phosphorus  is  checked,  that  is, 
its  slow  combustion  prevented.  To  this,  therefore, 
is  attributable  the  fact  that  the  voltaic  condition  of 
the  air  above  the  phosphorus  can  be  repeatedly 
altered,  and  depends  essentially  on  the  temperature ; 
so  that  this  air  is  sometimes  positive,  sometimes 
negative,  and  sometimes  neither.  I  may  mention  in 
passing,  that  according  to  my  experiments  the 


54  LETTEKS  OF  BEEZELIUS 

positive  polarity  of  this  air  is  chiefly  due  to  phos- 
phorus vapour,  and  also  partly  to  traces  of  hydrogen 
phosphide ;  and  it  is  easy  to  see  from  what  I  have 
said,  that  these  substances  would  exert  a  destructive 
action  on  the  ozone.  This  action  of  phosphorus 
vapour  may  easily  be  shown  by  putting  a  test  paper 
,first  into  it  and  then  into  an  atmosphere  of  ozone. 
As  long  as  any  traces  of  phosphorus  vapour  adhere 
to  the  paper  it  will  not  be  turned  blue.  Conversely, 
if  a  test  paper  is  turned  blue  by  ozone  and  then 
plunged  into  an  atmosphere  containing  phosphorus 
vapour,  the  blue  colour  disappears. 

Finally  I  must  mention,  that  if  ozone  is  breathed 
in  small  quantities  it  produces  on  the  organism  effects 
similar  to  those  produced  by  chlorine:  coughing, 
oppression  of  the  chest,  in  short,  all  the  symptoms  of 
a  cold.  A  mouse  placed  in  a  flask  filled  with  air  con- 
taining only  very  small  quantities  of  ozone  died  after 
five  minutes  in  violent  convulsions.  From  the  results 
described  above,  as  well  as  from  certain  other  facts 
which  I  have  discovered,  some  of  which  still  remain 
to  be  mentioned,  it  seems  to  me  that  we  may  con- 
clude with  a  fair  degree  of  certainty  that  nitrogen  is 
the  source  of  ozone,  or,  to  be  more  explicit,  that 
nitrogen  consists  of  ozone  and  hydrogen.  However 
different  the  circumstances  under  which  ozone  is 
formed  may  appear  at  first  sight,  there  is  yet  one 
condition  which  the  electric,  voltaic,  and  chemical 
methods  of  production  all  fulfil  alike,  and  that  is 
the  presence  of  nitrogen.  The  formation  of  ozone  by 
ordinary  electricity,  by  the  voltaic  current,  and  by 


AND  SCHONBEIN  55 

means  of  phosphorus  may  be  explained  as  follows : 

1.  Electrical  method  of  separation.     Just  as  ordinary 
electricity  decomposes  a  series  of  gaseous  hydrogen 
compounds,  especially  in  the  presence  of  oxygen,  so, 
when  it  is  discharged  from  a  point  into  the  air,  it 
determines  the  combination  of  the  oxygen  with  the 
hydrogen  contained  in  the  nitrogen  and  sets  free  the 
ozone.     If  instead  of  nitrogen  (i.e.,  hydrogen  ozonide) 
the  atmosphere  contained  hydrogen  chloride,  the  dis- 
charge of  electricity  into  the  air  would  also  produce  a 
smell,  the  feebler  smell  of  chlorine;  and,  moreover, 
the  chemical  actions  which  under  these  circumstances 
the  electrical  brush  would  produce,  would  be  quite 
analogous   to   those   which    are    actually   observed. 

2.  Voltaic  mode  of  production.     The  nitrogen,  that  is 
the  hydrogen   ozonide,   dissolved  in   water  is,  like 
hydrogen  chloride,  an  electrolyte.     It  is  decomposed 
by  the  current,  its  hydrogen  being  set  free  at  the 
negative  pole,  and  its  ozone  at  the  positive.     Boiled 
out  water,  i.e.,  water  free  from  nitrogen,  does  not  give 
the  smallest  trace  of  ozone  on  electrolysis,   but  if 
shaken  with   air  or  nitrogen,  then  on  passing   the 
current,  ozone  is  again  set  free  at  the  positive  pole. 
Hitherto  I  have  not  been  able  to  find  anything  at 
the   negative   pole   but  hydrogen.     I    may  mention 
here  that  the  presence  in  the  water  of  the  smallest 
quantities  of  sulphurous  acid,  hydrogen  sulphide,  and 
other  substances,  which  for  example  would  prevent 
the  electrolytic  liberation  of  chlorine,  also  stop  the 
formation  of  ozone.     Sometimes  even  distilled  water 
contains  substances  which  prevent  its  formation,  even 


56  LETTEES  OF  BEEZELIUS 

when  our  reagents  are  unable  to  detect  the  presence 
of  any  foreign  body  in  it.  3.  Chemical  method  of 
formation.  Phosphorus  in  a  state  of  slow  combustion 
exerts  a  catalytic  action  on  the  oxygen  and  nitrogen 
in  contact  with  it,  causing  the  former  to  combine 
with  the  hydrogen  of  the  latter  and  set  the  ozone 
free.  Part  of  this  ozone  appears  as  a  gas  and  mixes 
with  the  air,  while  another  part  combines  with  the 
phosphorus  to  form  phosphorus  ozonide,  which  is  de- 
composed by  the  water  present  into  phosphoric  acid 
and  hydrogen  ozonide,  i.e.,  nitrogen.  This  is  the 
reason  why  in  moist  atmospheric  air  the  oxidation 
of  phosphorus  proceeds  so  comparatively  fast,  and  it 
also  explains  the  fact,  that  in  the  slow  combustion  of 
phosphorus  in  air,  not  only  phosphorous  acid  is  pro- 
duced, but  also  phosphoric ;  the  latter  is  undoubtedly 
formed  by  means  of  ozone,  while  the  immediate 
result  of  the  slow  oxidation  of  the  phosphorus  is  the 
production  of  the  former. 

Similarly  in  the  light  of  the  facts  which  I  have 
discovered  we  can  understand  the  long  known  and 
remarkable  property  of  nitrogen,  of  supporting  the 
luminescence  of  phosphorus.  According  to  my  ex- 
periments, air  standing  over  phosphorus  and  calcium 
chloride  does  acquire  a  power  of  turning  my  test 
paper  blue,  but  very  little  ozone  is  formed  under  these 
conditions,  and  hence  very  little  phosphoric  acid, 
because  the  air  cannot  at  first  contain  any  water 
vapour,  and  the  water  produced  by  the  action  of  the 
oxygen  on  the  hydrogen  ozonide  is  mostly  absorbed 
by  the  calcium  chloride.  Probably  the  formation  of 


AND  SCHONBEIN  57 

phosphoric  acid  would  proceed  more  rapidly  in  a  dry 
atmosphere  in  which  no  calcium  chloride  was  placed 
than  in  air  containing  a  dehydrating  agent.  I  have 
not  yet  had  time  to  try  this  experiment. 

If  I  am  right  in  what  I  have  said,  and  there  can 
hardly  be  any  doubt  about  it,  the  whole  chemistry 
of  the  nitrogen  compounds  will  have  to  be  regarded 
from  a  totally  new  point  of  view,  and  in  particular 
nitric  acid  will  have  to  be  considered  as  ozonic  acid, 
a  theory  which  is  also  supported  by  the  great  simi- 
larity between  the  nitrates  and  the  chlorates,  etc. 
We  should  probably  have  to  consider  nitrogen  itself 
as  the  first  stage  of  the  hydrogenation  of  ozone,  the 
amides  being  the  second,  ammonia  the  third,  and 
ammonium  the  fourth.  I  need  not  point  out  what  an 
importance  nitrogen  would  have  for  meteorology  if  it 
were  hydrogen  ozonide.  Similarly  certain  diseases 
might  be  due  to  ozone,  and  so  forth. 

I  must  now  bring  my  letter  to  an  end,  and  reserve 
for  another  time  the  account  of  my  investigations.  It 
would  give  me  great  pleasure  if  you  would  communi- 
cate the  contents  of  my  letter  to  the  Stockholm 
Academy.  You  would  be  doing  me  the  greatest 
service  if  you  would  take  an  opportunity  soon  of 
giving  me  your  opinion  and  your  criticism  on  my 
experiments. 

With  the  utmost  respect,  I  have  the  honour  to  be, 
My  dear  Baron, 

Yours  most  sincerely, 

C.  F.  SCHONBEIN. 


58  LETTEES  OF  BEEZELIUS 

P.S.  1. — Of  the  enclosed  strips  of  litmus  paper  : 

No.  1  is  bleached  by  electrical  ozone. 
No.  2  by  voltaic  ozone. 
No.  3  by  chemical  ozone. 

P.S.  2. — I  must  add  that  I  have  obtained  potassium 
nitrate  by  treating  chemically-prepared  ozone  with 
potash  solution.  I  am  hoping  to  discover,  as  well  as 
potassium  ozonate,  i.e.,  nitrate,  potassium  ozonide.  It 
is,  no  doubt,  chemically  possible  that  ozone,  air,  and 
potash  may  give  potassium  nitrate.  But  at  any  rate 
the  fact  that  potassium  nitrate  is  found  under  these 
conditions  is  a  very  remarkable  phenomenon,  and 
seems  to  go  far  to  confirm  the  view  expressed  in  my 
letter  that  nitrogen  is  hydrogen  ozonide. 

An  extensive  extract  from  this  detailed  letter  was 
printed  in  the  fifth  number  of  the  first  year's  publication  of 
the  Ofversigt  af  Kongl.  Vetenskaps  Akademiens  forhand- 
lingar  of  15th  May  1844  [vol  i.,  p.  71-75],  and 
next  day  Berzelius  wrote  personally  to  Schb'nbein.  He 
thought  that  the  whole  ozone  question  was  still  waiting 
for  a  satisfactory  solution,  as  is  shown  by  the  remarks 
which  he  appended  to  Schonbein's  letter,  by  his  own 
letter,  and  still  more  clearly  from  the  Jdhresbericht. 
He  considered  ozone,  as  he  says  there,  to  be  a  "proble- 
matic body." 

We  need  not  be  surprised  at  Schonbein's  bold  assump- 
tion of  the  decomposition  of  nitrogen.  Berzelius  was 
just  the  man  whom  he  might  expect  to  encourage  him 
in  this  view,  for  in  his  inmost  heart  he  had  always 
believed l  in  the  compound  nature  of  nitrogen,  although 

1  Cf.  Kose,  Gedachtnisrede  auf  Berzelius,  Berlin  (1852),  p.  27. 


AND  SCHONBEIN  59 

he  was  no  longer  prepared  to  stand  by  the  assertion  he 
made  in  1818  "that  the  compound  nature  of  nitrogen  is 
not  to  be  regarded  merely  as  a  hypothesis,  but,  if  we  grant 
the  law  of  constant  proportions,  as  an  almost  established 
fact."  i 


XI 

Berzelius  to  Schbnbein 

STOCKHOLM,  IQth  May  1844. 

MY  DEAR  SIR, 

I  thank  you  sincerely  for  your  extremely 
interesting  letter  of  14th  April,  and  for  the  scientific 
novelties  which  it  contains.  In  accordance  with 
your  wish  I  laid  it  before  the  Koyal  Academy 
at  their  last  meeting,  and  they  ordered  that  an 
extract  from  it  be  printed  among  their  Transactions  of 
that  meeting. 

Now  that  you  are  able  to  produce  ozone  chemically 
you  could  surely  saturate  a  sufficient  amount  of  air 
with  it  to  enable  you  to  obtain  its  compounds  in 
weighable  quantities.  If,  for  example,  you  were  to 

1  Unersokning  of  Quafvets,  Vatets  och  Ammoniakens  natur. 
Hisinger  Afhandl.  i  Fysik,  vol.  v.  (1818)  p.  198  ;  Gilbert, 
AnnaL,  vol.  xlvi.  (1814)  p.  148.  Previously,  p.  133,  he  says  : 
"  But  my  object  is  to  prove  that  neither  Gay-Lussac's  analysis 
of  nitric  acid,  nor  my  own  statements  about  the  hyperbasic 
salts  considered  above  (the  reference  is  to  basic  lead  nitrate)  are 
right,  and  to  show  how  by  correcting  these  two  analyses  we  can 
remove  satisfactorily  all  the  objections  which  have  hitherto 
appeared  to  render  the  theory  of  the  compound  nature  of 
nitrogen  untenable." 


60  LETTEES  OF  BEEZELIUS 

put  into  your  large  glass  flask,  as  well  as  phosphorus, 
a  flat  vessel  containing  an  amalgam  of  silver,  lead, 
zinc  or  tin,  it  seems  to  me  that  the  metal  dissolved  in 
the  mercury  would  necessarily  combine  with  ozone 
to  form  a  metallic  ozonide,  and  the  compound  could 
thus  be  prepared  without  the  disturbing  influence  of 
water,  particularly  if  the  metal  chosen  were  one 
which  was  not  attacked  by  the  vapours  of  phos- 
phorous acid.  After  several  weeks  or  a  few  months 
an  arrangement  of  this  kind  might  give  a  sufficient 
quantity  of  the  substance  for  investigation. 

Your  theoretical  ideas  are  extremely  simple  and 
for  that  reason  one  would  be  glad  to  believe  in  them. 
On  the  other  hand  they  offer  great  difficulties.  What 
are  the  oxidation  products  of  nitrogen  if  J?  =  OzH  ? 
Are  they  OzH  +  1,  2,  3  and  5  atoms  of  oxygen  ?  In 
that  case  OzH  shows  an  inexplicable  difference  in 
character  from  the  ordinary  substances  which  form 
salts,  for  it  ought  to  be  a  strong  hydracid.  Again 
phosphorus,  arsenic,  and  antimony  form  compounds 
analogous  in  some  degree  to  ammonia;  but  all  of 
them  contain  three  equivalents  of  hydrogen,  while 
ammonia  would  have  to  be  written  OzH4. 

On  the  other  hand  if  nitric  oxide,  nitric  acid,  etc., 
are  to  be  Oz,  6z  the  theory  does  not  accord  with  the 
composition  of  these  bodies,  and  particularly  not  with 
their  densities,  the  experimental  values  of  which 
agree  so  exactly  with  those  calculated  from  their 
composition.  If  a  certain  quantity  of  hydrogen  gas 
were  driven  out  of  the  compound,  in  the  combination 
of  nitrogen  with  oxygen,  the  gaseous  product  so  formed 


AND  SCHONBEm  61 

should  have  a  decidedly  higher  density.  Indeed  I  do 
not  think  the  problem  is  yet  in  a  position  to  be 
solved.  You  must  submit  the  older  experiments  of 
Gottling  l  and  Bockmann  2  to  revision  ;  it  is  possible 
that  in  their  papers  on  the  luminescence  of  phos- 
phorus in  nitrogen  (particularly  in  that  of  the  latter, 
who  declares  that  nitrogen  disappears)  you  may  find 
facts  which  will  suggest  to  you  new  methods  of 
research.  The  investigation  is  so  important  that  you 
must  follow  it  up  with  the  true  Bunsen  perseverance,3 
and  not  abandon  it  until,  if  possible,  we  are  perfectly 
clear  about  it. 

I  wish  you  patience  and  good  luck  in  your  research  ; 
and  with  assurances  of  the  greatest  respect, 
I  remain, 

Yours  most  sincerely, 

JAC.  BERZELIUS. 


1  Johann  Friedrich  August  Gottling,  born  at  Derenburg  near 
Halberstadt  in  1755,   died  at  Jena   1809.     He  was  first  an 
apothecary,  and  then  professor  of  chemistry,  pharmacy,   and 
technology  at   Jena  :     "  Etwas  u'ber  den  Stickstoff  und  das 
Leuchten  das  Phosphors  in  Stickluft,"  Cfren.  Neues  Journ.,  vol. 
i.  (1795)  p.  1. 

2  Carl  Wilhelm  Bockmann,  born  at  Karlsruhe  in  1773,  died 
in  1821,  teacher  of  physics  at  the  gymnasium  there  :    "  Ver- 
suche    u'ber  das    Verhalten    des  Phosphors  in  verschiedenen 
Gasen,"  Erlangen,  1800. 

3  He  no  doubt  alludes  in  particular  to  Bunsen's  investigations 
on  cacodyl  which  were  begun  in  1837,  and  whose  conclusion 
Berzelius  had  announced  in  the  volume  of  the  Jahresbericht 
which  was  laid  before  the  Academy  on  31st  March. 


62  LETTEES  OF  BERZELIUS 

XII 
Schonbein  to  Berzelius 

MY  DEAR  BARON, 

Since  you  considered  my  papers  on  ozone 
worthy  of  your  attention,  I  flatter  myself  that  you 
will  be  interested  to  hear  of  the  results  of  my  investi- 
gations on  a  kindred  subject.  Owing  to  want  of 
space  I  will  confine  myself  to  general  outlines, 
especially  as  a  detailed  account  of  the  substance  in 
question  will  shortly  be  published.1  The  combustion 
of  phosphorus  in  atmospheric  air  and  the  formation 
of  a  highly  electro-negative  body  possessed  of  marked 
oxidizing  properties,  my  ozone,  directed  my  attention 
to  the  combustion  in  air  of  bodies  generally,  especially 
to  cases  analogous  to  the  gradual  oxidation  of  phos- 
phorus, such  as  the  partial  combustion  of  ether 
vapour  at  comparatively  low  temperatures.  By 
analogy,  and  in  accordance  with  my  theoretical 
views  as  to  the  nature  of  nitrogen,  I  anticipated  the 
formation  of  a  body  with  electro-negative  and  oxidiz- 
ing properties.  You  will  see  that  my  results  show 
that  the  gradual  oxidation  of  ether  vapour  (as  well  as 
the  rapid  burning  of  bodies  in  general)  is  accompanied 
by  phenomena  which  so  far  have  escaped  the  notice 
of  chemists,  but  which  certainly  appear  to  me  to  be 

1  "  Uber  die  langsame  und  rasclie  Verbrennung  der  Korper 
in  atmospharischer  Luff     Bale,  1845.     Dated  5th  June  1845. 


AND  SCHONBEIN  63 

well  worth  careful  attention.  When  a  mixture  of 
ether  vapour  with  atmospheric  air  is  partially  burnt 
by  means  of  a  moderately  heated  platinum  wire, 
a  substance  is  formed  which  has  the  following 
properties : —  * 

1.  It  decolorizes  indigo  solution. 

2.  It  decomposes  potassium  iodide  and  hydrogen 

iodide,  setting  iodine  free,  thus  turning  paper 
moistened  with  starch  and  potassium  iodide 
blue. 

3.  It  decomposes  potassium  bromide,  though  not 

very  readily. 

4.  It  converts  potassium  ferrocyanide  into  the  red 

prussiate  of  potash. 

5.  It  immediately  imparts  a  deep  colour  to  white 

ferrous  cyanide. 

6.  It  changes  ferrous  into  ferric  salts. 

7.  In  the  presence  of  water  it  oxidizes  iodine  to 

iodic  acid. 

8.  In  presence  of  water  it  changes  sulphurous  into 

sulphuric  acid. 

9.  It  readily  decolorizes  sulphide  of  lead  and  other 

metallic  sulphides,  apparently  converting 
them  into  sulphates. 

10.  It  renders  an  aqueous  solution  of  sulphuretted 

hydrogen  unable  to  precipitate  lead  salts. 

11.  A    concentrated    solution    of    the    substance, 

possessing  all  the  aforementioned  properties, 


64  LETTEKS  OF  BEEZELIUS 

loses  them  so  soon  as  it  is  brought  in  contact 
with  oxidizable  substances,  e.g.,  sulphurous 
acid  or  metals. 

12.  Even   mercury    reacts  in  this   way,   with   the 
formation  of  a  mercury  salt  soluble  in  water. 

If  hydrogen  is  burned  in  atmospheric  air  and  the 
following  liquids  are  held  over  the  point  of  the  flame 
in  narrow  tubes,  the  following  reactions  take  place : — 

1.  Indigo  solution  becomes  decolorized. 

2.  Iodine  is  liberated  from  potassium  iodide  and 

hydrogen  iodide  solutions  or  paper  moistened 
with  starch  paste  and  potassium  iodide  be- 
comes blue. 

3.  A  potassium  ferrocyanide  solution  assumes  an 

intense  yellow  coloration,  is,  in  fact,  converted 
into  potassium  ferricyanide. 

.  4.  White  ferrous  cyanide  suspended  in  water  turns 
dark  blue. 

5.  A  ferrous  salt  in  solution  is  converted  into  a 

ferric  salt. 

6.  Aqueous   sulphurous   acid  is  transformed  into 

sulphuric  acid. 

7.  Lead  sulphide  suspended  in  water  is  bleached. 

A  slip  of  paper  saturated  with  water  and 
coloured  brown  with  lead  sulphide  turns 
white  on  being  held  over  the  point  of  the 
flame. 


AND  SCHONBEIK  65 

The  very  same  reactions,  only  in  a  more  pronounced 
degree,  can  be  brought  about  with  the  help  of  the 
flame  of  an  ordinary  candle,  by  merely  leading  into 
it  a  current  of  atmospheric  air  as  in  testing  with  the 
blow-pipe.  Thus  the  remarkable  fact  appears  that 
the  results  are  due  to  the  oxidizing,  and  under  no 
circumstances  to  the  inner  or  reducing  flame.  The 
simplest  method  of  demonstrating  one  of  these  re- 
actions is  to  draw  a  strip  of  paper,  wetted  with  water 
and  saturated  with  starch  paste,  through  the  oxidiz- 
ing flame  ;  wherever  the  latter  touches  it,  it  becomes 
as  blue  as  if  it  had  been  exposed  to  the  action  of 
electricity.  In  the  reducing  flame  on  the  other  hand 
this  coloration  vanishes  immediately. 

I  also  blew  a  current  of  air  through  a  phosphorus 
flame,  and  I  got  indications  of  the  occurrence  of  the 
above  reactions;  starch  and  potassium  iodide  in 
particular  become  blue  in  the  neighbourhood  of  the 
tip  of  the  flame.  The  flames  of  camphor  and  other 
similar  bodies  of  course  resemble  that  of  an  ordinary 
candle.  The  fact  that  in  a  sulphur  flame  such 
oxidizing  agents  are  not  formed  is  explained  by  the 
presence  of  sulphurous  acid  ;  and  in  this  connection 
it  is  remarkable  that  water,  upon  which  a  sulphur 
flame  is  allowed  to  play  by  means  of  a  blow-pipe,  in- 
variably contains  an  appreciable  quantity  of  sulphuric 
acid. 

The  results  of  my  investigations  therefore  go  to 
show  that  any  body,  when  burned  in  atmospheric 
air,  produces  an  electro-negative  oxidizing  substance. 
But  whether  all  forms  of  combustion  give  the  same 


8  H  A 
OF  THE 


(  UNIVERSITY  I 


66  LETTEES  OF  BEEZELIUS 

substances,  that  is  to  say,  whether  the  substances 
formed  by  the  gradual  oxidation  of  phosphorus 
and  of  ether  vapour  are  identical  with  those 
produced  by  the  rapid  combustion  of  the  other 
bodies,  must  be  decided  by  further  investigations. 
At  any  rate  this  important  fact  remains,  that  the 
substances  in  question  show  a  remarkable  resemblance 
to  one  another  in  their  properties.  That  they  have 
nothing  in  common  with  nitric  or  nitrous  acid,  is 
obvious  from  the  way  in  which  they  are  produced ; 
but  there  are  also  other  reasons  which  go  against  this 
assumption.  The  facts  I  have  mentioned  hardly  over- 
throw my  hypothesis  as  to  the  nature  of  nitrogen; 
they  go  to  show  that  high  temperatures  would  cause 
the  oxygen  of  the  air  to  combine  with  the  hydrogen 
of  the  nitrogen  and  set  ozone  free ;  this  may  be  com- 
pared to  the  way  in  which  I  imagine  the  catalytic 
influence  of  phosphorus  or  ordinary  electricity  would 
act  on  a  mixture  of  oxygen  and  nitrogen.  However, 
I  do  not  wish  to  attach  any  great  importance  to  this 
view,  but  only  add  that  such  results  possess  a  peculiar 
interest  in  regard  to  the  opposite  chemical  effect 
caused  by  the  two  parts  of  the  blow-pipe  flame.  I 
have  no  doubt  that  the  oxidizing  power  of  the  outer 
flame  is  due  to  some  peculiar  substance  and  not 
directly  to  ordinary  heated  oxygen. 

I  should  of  course  be  glad  if  you  would  communi- 
cate the  contents  of  this  letter  to  your  Academy,  if 
you  think  it  of  sufficient  importance. 

I  hope  that  this  note  will  find  you  in  good  health, 


AND  SCHONBEIN  67 

and  I  trust  that  you  will  honour  me  soon  with  a  few 
lines  in  reply. 

With  the  profoundest  respect,  I  have  the  honour  to 

remain, 

Yours  most  obediently, 

C.  F.  SCHONBEIN. 

P.S. — I  trust  you  have  received  my  paper  on  ozone. 
BALE,  15th  January  1845. 


This  letter  also  was  read  at  the  Academy  in  Stockholm, 
and  a  summary  of  it  appeared  in  the  Ofversigt  of  Kongl. 
Vetenskaps  Akadamiens  forhandlingar  [vol.  2.  (1845) 
p.  1.8].  Two  days  after  this  meeting,  which  took  place 
on  12th  February,  Berzelius  sent  the  following  reply 
to  Schonbein : — 


XIII 
Berzelius  to  Schonbein 

STOCKHOLM,  \Uh  February  1845. 

DEAR  SIR, 

I  thank  you  very  much  for  your  interesting 
communication  in  your  last  letter  of  15th  January, 
which  I  read  before  the  Academy  and  which  they 
are  publishing  in  their  Transactions.  I  think  you 
have  proved  that  ozone  is  always  formed  during 
combustions  in  atmospheric  air ;  hence  there  only 


68  LETTEES  OF  BEEZELIUS 

remains  the  further  step  of  producing  an  unmistak- 
able compound  of  this  body  with  some  other  in  such 
quantity  as  to  make  it  possible  to  study  its  properties 
accurately.  If  you  lead  a  current  of  air  first  through 
ether  and  then  through  platinum  sponge — this  can 
readily  be  effected  by  means  of  an  aspirator,  and 
continued  for  weeks  together — you  might  collect  a 
considerable  quantity  of  the  products  of  combustion ; 
they  would  be  little  else  than  water,  carbonic  acid 
and  ozone.  If,  as  you  state,  the  liquid  dissolves 
mercury,  forming  a  soluble  salt,  you  might  condense 
it  over  mercury  and  thus  obtain  a  quantity  of  the 
mercury  salt,  whose  properties  could  then  be 
investigated. 

I  did  not  get  your  detailed  paper,  but  I  am 
acquainted  with  it  from  the  French  translation  in 
de  la  Eive's  Archive  de  I' filectriciU.1  I  candidly 
confess  that  I  am  not  quite  satisfied  with  the  experi- 
mental part  of  it ;  in  the  first  place  the  preparation 
of  the  potassium  salt  is  tremendously  laborious,  and 
in  the  next  place  the  reactions  which  you  have 
performed  with  the  new  salt  are  not  carried  out 
on  correct  principles.  For  you  assert  that  all 
acids  evolve  from  it  an  odour  of  ozone,  the  acid 
uniting  with  the  potassium.  This  is  much  as 
though  sulphuric  acid  were  to  produce  a  smell  of 
chlorine  with  common  salt.  You  should  have  tried 
it  with  chlorine  or  bromine  water  in  order  to  set 
ozone  free.  If,  however,  which  I  do  not  doubt,  your 
assertion  be  correct,  the  odour  must  be  due  to  hydro- 
5  V Electricity  vol.  iv.  (1844)  p.  333. 


AND  SCHONBEIN  69 

ozonic  acid ;  now  if  such  an  acid  does  exist  and  can 
be  prepared,  it  seems  fairly  evident  that  nitrogen 
cannot  be  hydrogen  ozonide.  It  would  therefore  be 
better  to  put  on  one  side  all  theoretical  conjectures 
as  to  the  constitution  of  ozone  and  nitrogen  and  to 
study  the  properties  of  ozone  itself.  When  once  you 
have  caught  it,  it  will  be  easier  to  theorize  about  it. 
I  hope  you  will  excuse  my  candid  remarks. 

With  the  kindest  regards, 

I  have  the  honour  to  remain, 

Yours  obediently, 

JAC.  BERZELIUS. 

From  the  postmark  this  letter  reached  Bale  on  the  26th 
of  February ;  Schonbein  therefore  answered  it  by  return 
of  post. 


XIV 
Schonbein  to  Berzelius 

MY  DEAR  BARON, 

I  must  ask  you  to  forgive  me  for  troubling  you 
so  soon  with  another  letter  ;  but  some  remarks  which 
you  were  so  good  to  make  on  my  larger  research  con- 
cerning ozone,  in  your  honoured  letter  of  the  14th  of 
last  month,  have  induced  me  to  send  you  a  few  words 
in  reply.  In  the  first  place  I  take  the  liberty  of  re- 
marking that  the  paper  in  question,  in  the  last 
number  of  de  la  Eive's  Archives,  absolutely  teems 


70  LETTEES  OF  BEEZELIUS 

with  errors  of  translation,  so  that  in  some  cases  its 
meaning  is  the  exact  opposite  of  that  of  the  German 
original. 

In  my  paper  the  salt  obtained  by  the  complete 
decomposition  of  potassium  iodide  by  means  of  ozone 
was  not  said  to  be  pure  potassium  ozonide  (although 
I  was  certainly  inclined  at  first  to  think  it  was  that) ; 
on  the  contrary  it  was  expressly  stated  that  it  con- 
tained potassium  iodate.1  Also  I  have  nowhere  said, 
as  far  as  I  know,  that  all  acids  gave  with  this  salt 
a  smell  of  ozone.  I  did  indeed  remark  that  sulphuric 
acid  set  free  from  it  a  constituent  which  had  a  smell 
apparently  intermediate  between  that  of  bromine  and 
that  of  iodine,  and  which  turns  potassium  iodide 
starch  paste  blue,  etc.,  but  I  did  not  venture  de- 
finitely to  ascribe  this  smell  to  ozone,  though  I 
expressed  an  inclination  to  believe  that  it  was  due  to 
it.  Assuming  that  the  salt  in  question  contains 
some  potassium  iodate  as  well  as  potassium  ozonide, 
I  expressed  myself  to  the  following  effect  as  to  the 
supposed  development  of  ozone,  on  pages  116  and  117 
of  the  German  paper2:  "The  production  of  ozone 
from  this  mixture  of  salts  by  means  of  sulphuric  acid, 
the  brown  colour  which  the  acid  causes,  and  the 
evolution  of  iodine  vapours  on  warming,  are  satis- 
factorily explained  if  we  suppose  that  the  salt  in 
question  is  a  mixture  of  potassium  iodate  and 

1  Cf.  also  Berzelius'  remarks  in  the  Jahresbericht,  vol.  xxv. 
(1846)  p.  132. 

3  Schonbein  is  here  referring  to  the  earlier  paper  :  Uler  die 
Erzeugung  des  Ozons. 


AND  SCHONBEIN  71 

potassium  ozonide.  The  sulphuric  acid  separates  the 
iodic  acid  from  the  potash,  and  part  of  the  oxygen  of 
the  latter  acid  combines  with  the  potassium  of  the 
ozonide,  setting  free  iodine  and  ozone."  This  single 
passage  is,  I  think,  sufficient  to  place  the  point  in 
question  in  the  right  light.  It  was  not  because  I 
had  not  thought  of  the  method  that  I  did  not  treat 
my  salt  with  chlorine.  But  I  only  had,  so  to  speak, 
homoeopathic  quantities  of  the  salt,  and  so  I  could 
only  perform  a  few  incomplete  experiments  with  it ; 
and  as  I  wished  to  see  whether  I  could  obtain  from 
it  a  body  similar  in  its  reactions  to  chlorine  or  ozone, 
I  intentionally  abstained  from  employing  the  former. 
Originally  I  mixed  my  salt  with  pure  manganese 
dioxide,  and  then  on  treating  it  with  sulphuric  acid 
I  obtained  the  reactions  I  have  described;  but  I 
found  out  later  that  the  manganese  dioxide  was 
quite  unnecessary,  and  that  the  reaction  was  due  to 
the  presence  of  potassium  iodate.  The  fact  that  a 
solution  of  the  salt,  when  treated  with  any  acid 
colours  starch  paste  containing  potassium  iodide  blue, 
likewise  makes  the  presence  of  potassium  iodate  con- 
ceivable. However,  I  do  not  attach  any  importance 
to  these  preliminary  experiments,  since  they  were 
performed,  as  I  have  said,  with  such  small 
quantities. 

You  are  quite  right  in  saying  that  the  plan  which 
I  have  adopted  of  using  potassium  iodide  to  absorb 
the  ozone,  liberated  by  means  of  phosphorus,  is  very 
laborious,  but  I  am  bound  to  say  that  up  to  the 
present  moment  I  know  of  no  better.  Mercury,  for 


72  LETTEES  OF  BEKZELIUS 

instance,  takes  such  an  endless  time  to  absorb  ozone, 
set  free  by  phosphorus,  that  I  can  hardly  believe  it 
will  ever  be  employed  as  a  means  of  separating  it. 
At  all  events  the  fact  is,  that  there  is  no  material 
which  is  able  to  take  up  ozone  more  rapidly  than 
potassium  iodide.  I  willingly  admit  that  you  are  quite 
right  in  blaming  me  for  indulging  in  my  paper  in  too 
much  speculation  about  ozone ;  I  will  not  attempt  to 
justify  this  offence  even  by  saying  that  it  is  never  so 
often  committed  as  in  chemistry,  as  has  been  amply 
shown  in  recent  times.  I  am  sure  that  you  will 
readily  grant  that  the  circumstances  under  which 
ozone  is  produced  inevitably  lead  one  to  think  of  the 
possibility  of  nitrogen  being  a  compound.  However 
baseless  my  hypothesis  as  to  the  nature  of  this  body 
may  be,  it  has  guided  me  in  all  the  experiments  I 
have  hitherto  made,  and  has  led  me  to  a  series  of 
discoveries.  Whatever  ozone  may  prove  to  be,  this 
much  seems  to  me  to  be  certain,  from  its  voltaic  and 
chemical  properties,  that  it  is  not  a  hydrogen  com- 
pound or  at  least  not  a  hydracid. 

As  soon  as  I  am  quite  well  again  I  shall  continue 
my  experiments  on  ozone  with  renewed  zeal ;  but  I 
have  for  some  time  been  condemned  to  inaction  in 
consequence  of  a  cold  which  I  have  no  doubt  that  I 
caught  through  breathing  too  much  of  the  gases 
produced  by  the  slow  combustion  of  ether 
vapour. 

I  have  for  a  long  time  been  very  anxious  to  visit 
your  beautiful  country,  and  as  soon  as  I  am  able  to 
carry  out  my  project  I  shall  lose  no  time  in  doing  so  ; 


AND  SCHONBEIN  73 

in  which  case  I  shall  take  the  liberty  of  paying  my 
respects  to  you  in  person. 

With  the  greatest  esteem, 
I  have  the  honour  to  be,  my  dear  Baron, 

Yours  most  sincerely, 

C.  F.  SCHONBEIN. 
BALE,  1st  March  1845. 


The  following  letter  was  written  to  Berzelius  three 
weeks  later,  and  communicated  to  the  Royal  Academy  of 
Stockholm  at  their  meeting  of  April  the  9th,  together 
with  a  letter  written  by  Plantamour  of  Geneva  on 
February  the  4th,  describing  Marignac's  first  work  on 
ozone.  In  this  letter  there  is  as  yet  no  allusion  to  the 
possibility  of  ozone  being  a  form  of  oxygen.  This  was 
first  suggested  in  another  letter  of  Plantamour's  of  the 
20th  of  April  of  the  same  year,  which  was  laid  before  the 
Academy  on  the  21st  of  May,  and  printed  in  the  Ofver- 
sigt,  Arg.  2  (1845)  p.  116. 


XV 
Schbnbein  to  Berzelius 

MY  DEAR  BARON, 

I  believe  I  have  at  last  succeeded  in  solving 
the  ozone  riddle  ;  and  I  think  you  and  your  colleagues 
of  the  Eoyal  Academy,  as  you  have  attached  some 
importance  to  the  subject,  will  find  the  following 
communication  worthy  of  your  attention. 


74  LETTEES  OF  BEEZELIUS 

After  all  my  attempts  to  isolate  ozone  had  failed, 
and  I  had  never  got  any  results  save  oxidations,  I 
was  induced  to  reconsider  the  conditions  under  which 
ozone  is  produced.  Five  years  ago,  when  I  prepared 
ozone  voltaically,  my  first  idea  was  that  it  was  a  body 
in  a  higher  state  of  oxidation ;  and  so  starting  again 
from  this  view  I  investigated  the  part  which  water 
plays  in  the  production  of  the  substance.  I  found 
that  by  the  action  of  atmospheric  air  on  phosphorus 
in  contact  with  water  at  30°,  ozone  is  produced  in 
larger  quantities  than  in  any  other  case,  and  moreover 
that  its  production  is  continually  diminished  as  the 
air  approaches  nearer  to  dryness.  Just  the  same 
results  were  obtained  if  I  performed  the  experiment 
with  a  mixture  of  ozone  and  carbonic  acid,  but  no 
ozone  was  produced  if  oxygen  alone,  or  nitrogen,  or 
carbon  dioxide  was  allowed  to  act  on  the  phosphorus. 
It  seemed  therefore  as  if  ozone  was  produced  from 
oxygen  and  water,  and  as  if  nitrogen  played  no 
essential  part  in  its  formation. 

As  much  as  five  years  ago  I  published  my  observa- 
tions that  the  discharge  of  electricity  from  a  heated 
point  did  not  produce  the  so-called  electrical  smell, 
and  that  the  voltaic  current  was  not  able  to  set  free 
any  ozone  from  heated  water.1  Similarly  I  found 
that  a  heated  platinum  strip  held  in  the  discharge 
from  a  cold  point  receives  no  negative  charge,  just  as 
happens  when  the  point  is  hot  and  the  strip  cold. 
Therefore,  proceeding  on  the  hypothesis  that  ozone 
may  be  a  higher  oxidation  product  of  hydrogen  which 
1  Poggend.  Annal.,  vol.  1.  (1840)  p.  618. 


AND  SCHONBEIN  75 

is  decomposed  by  heat,  I  made  the  following  experi- 
ments. Ozone  was  produced  in  a  large  flask  by  the 
usual  chemical  method  in  as  large  quantities  as 
possible,  and  a  suitable  arrangement  was  made 
whereby  the  atmosphere  charged  with  ozone  was 
caused  to  pass  through  a  narrow  glass  tube  into  the 
air.  As  long  as  the  tube  was  not  heated,  the  issuing 
air  had  a  smell  quite  indistinguishable  from  that 
noticed  in  the  neighbourhood  of  a  point  from  which 
electricity  is  being  discharged,  and  it  also  produced 
all  the  chemical  and  voltaic  reactions  which  are 
characteristic  of  chemical,  voltaic  and  electrical  ozone. 
Thus  it  gave  a  negative  charge  to  platinum,  it  turned 
starch  paste  containing  potassium  iodide  blue,  it 
destroyed  vegetable  colours,  etc.  But  if  about  an 
inch  of  the  tube  is  heated  by  means  of  a  spirit  lamp 
the  peculiar  smell  disappears,  and  at  the  same  time 
the  air  loses  all  its  peculiar  properties.  If  the  tube 
is  allowed  to  cool  again,  all  these  properties  reappear. 
Voltaic  ozone  of  course  behaves  in  exactly  the  same 
way  under  the  same  conditions.  The  complete 
similarity  of  the  action  of  heat  on  chemical,  voltaic 
and  electrical  ozone  may  serve  as  a  further  proof  of 
the  identity  of  these  substances. 

A  few  days  ago  my  friend  Marignac  l  of  Geneva 
informed  me  of  the  results  of  the  experiments  which 
he  has  carried  out  with  a  view  to  the  isolation  of 
ozone  and  the  determination  of  its  properties.  They 

1  Jean  Charles  Galisard  de  Marignac,  born  at  Geneva  in 
1817,  died  in  1894.  Professor  of  chemistry  at  the  University 
of  Geneva  from  1842  to  1878. 


76  LETTEES  OF  BEKZELIUS 

are  so  interesting  that  I  venture  to  communicate 
them  to  you.  This  distinguished  chemist  obtains 
from  water  completely  freed  from  air  and  acidified 
with  pure  sulphuric  acid,  large  quantities  of  ozone  if 
the  liquid  is  kept  cool.  Finely  divided  silver,  which 
rapidly  absorbs  ozone,  forms  with  it  nothing  but 
silver  oxide ;  potassium  iodide  gives  only  potassium 
iodate  and  some  carbonate.  He  fails,  as  I  did,  to  get 
any  ozone  with  pure  oxygen  or  with  carbonic  acid 
or  nitrogen,  but  he  obtains  it  from  both  the  two 
last-named  gases  as  well  as  from  hydrogen,  if  they 
contain  free  oxygen.  It  is  easy  to  see  by  comparing 
Marignac's  results  with  mine,  that  the  two  series 
supplement  and  confirm  one  another,  and  I  think  we 
may  fairly  conclude  from  them,  that  oxygen  and 
hydrogen  are  the  constituents  of  ozone,  and  that  the 
latter  is  formed  whenever  oxygen  comes  in  contact 
with  water  under  the  requisite  conditions.  The  pro- 
duction of  ozone  in  the  electrolysis  of  water  can  easily 
be  understood ;  to  explain  the  action  of  phosphorus 
and  electricity,  we  must  suppose  that  they  exert  a 
catalytic  influence  on  the  oxygen  and  the  water.  The 
following  facts  seem  to  make  it  certain  that  ozone  is 
not  identical  with  The'nard's  hydrogen  peroxide.1 
The  latter  has  no  smell,  dissolves  in  water  in  all  pro- 
portions, communicates  to  platinum,  according  to 
Becquerel's  and  my  own  observations,  a  positive 
charge,  and  is  converted  by  the  catalytic  action  of 

1  Th^nard,  "  Memoire  sur  la  combiuaison  de  1'oxigene,  et  sur 
les  propri£t£s  extraordinaires  que  possede  1'eau  exigence," 
Memoires  de  PAcadJmie,  Paris,  vol.  iii.  (1820)  p.  385. 


AND  SCHONBEIN  77 

silver  into  water  and  oxygen :  whereas  ozone  is  dis- 
tinguished by  a  highly  characteristic  smell,  scarcely 
dissolves  in  water  even  in  traces,  charges  platinum 
negatively,  and  oxidizes  silver.  Since  ozone  is  pro- 
duced by  the  influence  of  electricity  in  atmospheric 
air,  and  since  restorations  of  electrical  equilibrium 
are] continually  occurring,  it  follows  that  the  air  must 
contain  ozone.  Now  in  the  open  air  starch  paste 
containing  potassium  iodide  turns  blue,  and  potassium 
iodide  forms  the  iodate  with  the  liberation  of  iodine 
(though  only  to  a  small  extent) ;  and  since  in  a  closed 
vessel  none  of  these  phenomena  occur,  and  since  they 
are  produced  by  the  action  of  ozone  on  potassium 
iodide,  it  would  seem  that  we  ought  to  ascribe  them 
to  the  atmospheric  ozone.  But  if  so,  many  slow  oxi- 
dations which  take  place  in  the  air,  such  as  bleaching 
and  various  other  similar  phenomena,  must  also  be  due 
to  the  atmospheric  ozone,  and  not  to  the  free  oxygen 
of  the  air.  From  the  powerful  physiological  effects 
of  ozone,  its  presence  in  the  air  may  have  a  medical 
interest.  The  luminescence  of  phosphorus  in  atmos- 
pheric air,  which  has  so  long  been  known  and  is  so 
little  understood,  can  now  be  explained  fairly  satis- 
factorily. The  catalytic  influence  of  the  phosphorus 
determines  the  combination  of  the  oxygen  and  the 
water  to  form  ozone,  which  in  its  turn  oxidizes  the 
phosphorus  to  phosphoric  acid.  The  simultaneous 
production  of  phosphorous  acid  is  no  doubt  due  to 
the  direct  combination  of  the  atmospheric  oxygen 
with  the  phosphorus.  In  absolutely  dry  air  the 
luminescence  of  phosphorus  is  excessively  feeble,  and 


78  LETTEES  OF  BEEZELIUS 

no  ozone  is  formed,  from  which  it  would  seem  to 
follow  that  the  production  of  light  depends  chiefly 
on  the  oxidation  caused  by  the  ozone.  At  least  it  is 
a  fact  that  the  amount  of  ozone  formed  is  exactly 
proportional  to  the  intensity  of  the  luminescence1 
of  the  phosphorus.  The  great  similarity  between 
ozone  and  chlorine  leads  one  to  think  of  the  old  views 
about  the  latter,  and  it  is  possible  that  sooner  or  later 
this  hypothesis,  which  you  supported  for  so  long,  may 
again  become  the  subject  of  discussion. 

Pray  communicate  the  contents  of  this  letter  to 
the  Eoyal  Academy  if  you  find  it  sufficiently  interest- 
ing. 

With  the  greatest  respect, 
I  have  the  honour  to  remain,  my  dear  Baron, 
Yours  very  sincerely, 

C.  F.  SCHONBEIN. 


BiLE,  mnd  March  1845. 


It  seems  from  this  letter,  from  the  paper,  "Uberdie 
Natur  des  Ozons"  [Poggend.  Annal,  vol.  Ixv.  (1845) 
p.  69],  which  is  dated  Holy-Thursday,  1845,  i.e.,  20th 
March,  and  from  the  simultaneous  publication  of  the  two 
works  in  the  Archives  de  VMedridte,  vol.  v.,  Marignac, 
pp.  5-11  ;  Schonbein,  pp.  11-23,  that  Schonbein  was  not 

1  We  do  not  yet  know  why  the  catalytic  influence  of  phos- 
phorus is  not  exerted  in  oxygen  of  the  ordinary  density,  but 
only  when  the  gas  is  rarefied  to  a  certain  extent  either  by  itself 
or  by  dilution  with  certain  other  gases.  [This  note  is  by 
Schonbein.] 


AND  SCHONBEIN  79 

led  to  his  new  view  as  to  the  nature  of  ozone  by  Marignac, 
but  only  confirmed  in  it  by  the  simultaneous  work  of  the 
latter.1 


XVI 
Schonbein  to  Berzelius 

MY  DEAR  BARON, 

I  take  the  liberty  of  sending  you,  by  favour 
of  Herr  von  Mitscherlich,  two  papers  which  I  have 
just  published  on  ozone  and  kindred  subjects.  I 
hope  you  will  receive  them  with  indulgence,  as  a 
slight  mark  of  my  unbounded  esteem. 

I  have  for  some  time  been  busy  with  experiments 
on  the  formation  of  nitric  acid,  and  I  have  been 
successful  in  discovering  some  facts  which  appear 
to  me  to  throw  a  certain  amount  of  light  on  this 
subject,  which  has  hitherto  been  very  imperfectly 
understood.  I  have  come  to  the  conclusion  that  the 
production  of  nitric  acid  is  closely  connected  with 
the  action  of  ozone ;  it  seems  that  the  latter,  under 
some  conditions,  can  oxidize  nitrogen  to  nitric  acid. 
This  much  is  certain,  that  nitric  acid  is  formed  in 
the  production  of  ozone  in  atmospheric  air  by  the 
chemical  method  (by  the  means  of  phosphorus),  just 
as  it  is  by  passing  electric  sparks  through  a  moist 
mixture  of  oxygen  and  nitrogen.  This  is  evident 

1  Cf.  Engler,  "  Historisch-Kritische  Studie  iiber  das  Ozon " 
(reprint  from  the  Leopoldina\  Halle  (1879),  p.  8. 


80  LETTEES  OF  BEEZELIUS 

from  the  fact  that  the  so-called  phosphoric  acid, 
produced  by  the  phosphorus  in  moist  air,  always 
contains  nitric  acid.  I  shall  soon  publish  in 
Poggendorff's  Annalen  some  more  details  on  this 
not  uninteresting  subject.  You  may  possibly  be 
interested  to  have  a  little  sample  of  the  bleaching 
action  of  ozone,  and  so  I  have  taken  the  liberty  of 
enclosing  two  strips 1  of  linen,  one  of  which  has  been 
hung  for  about  a  fortnight  in  air  which  has  been 
ozonized  by  means  of  phosphorus.  The  second  is 
a  sample  of  the  unbleached  stuff.  I  must  add  that 
the  bleaching  of  the  white  strip  was  accomplished 
solely  by  means  of  ozonized  air. 

I  am  still  wholly  unable  to  understand  how  they 
can  have  found  in  the  Giessen  laboratory  that  by 
the  action  of  phosphorus  on  moist  air  no  substance 
is  produced  which  bleaches,  decomposes  potassium 
iodide,  and  in  other  ways  shows  itself  a  strong 
oxidizing  agent.  I  confess  that  the  experiments 
have  been  performed  there  in  a  way  which  could  not 
lead  to  any  but  negative  results. 

We  had  almost  persuaded  ourselves  here  that  on 
the  occasion  of  your  recent  visit  to  Germany  we 
should  have  the  pleasure  of  seeing  you  in  our  house, 
and  we  had  made  preliminary  arrangements  to  do 
you  honour;  but  unfortunately  these  hopes,  which 
were  based  on  the  statement  of  a  man  from  Berlin, 
have  not  been  realized. 

Indulging    in   the   pleasant   expectation   of    soon 

1  Both  strips  are  still  enclosed  in  the  letter. 


AND  SCHONBEIN  81 

being  honoured  by  a   letter   from  you,   I    beg    to 
remain,  my  dear  Baron, 

Yours  most  sincerely, 

C.  F.  SCHONBEIN. 

BALE,  SQtJi  September  1845. 


XVII 

Schbnbein  to  Berzelius 

MY  DEAR  BARON, 

In  the  course  of  my  latest  experiments  on 
ozone,  I  have  obtained  some  results  of  a  rather  unusual 
kind,  which  I  think  are  not  wholly  without  import- 
ance to  science.  In  particular  I  have  succeeded  in 
producing  a  most  remarkable  change  in  a  series  of 
organic  bodies ;  for  example,  I  have  converted  sugar 
into  a  resin,  that  is,  into  a  substance  soluble  in  ether, 
alcohol,  fatty  oils,  etc.,  but  insoluble  in  water.  One 
of  the  most  peculiar  transformations  that  I  have 
effected  is  in  vegetable  fibre,  which  I  have  brought 
into  such  a  condition  that  it  is  readily  soluble  in 
ether  and  alcohol,  but  unaffected  by  water,  and  if 
properly  prepared,  possesses  the  transparency  of  glass. 
On  this  change  of  vegetable  fibre  I  have  founded 
a  process  which  enables  me  to  convert  ordinary 
unsized  paper  into  a  substance  having  the  following 
properties. 


82  LETTEES  OF  BEKZELIUS 

1.  However  long  it  is  exposed  to  the  action  of 
water  it  retains  its   coherence,  which,  moreover,  is 
so  much  increased  by  my  process  that  the  paper  has 
a  texture  like  that  of  parchment. 

2.  Also,  acid  and  alkaline  solutions,  as,  for  example, 
water  containing  hydrochloric  acid  or  potash,  have 
no  destructive  action  on  the  prepared  paper ;  and  so 
ordinary  and  printing  ink  can  be  removed  from  it 
without  injury  to  its  durability. 

3.  Thin  and  extremely  brittle  paper  acquires,  by 
my  process,  a  firmness  and  toughness  equal  to  that 
of   much  thicker   ordinary   paper    of    the   toughest 
texture. 

4.  No  size  or  starch  is  required  to  make  it  avail- 
able for  printing  and  writing.     It  takes  ordinary  and 
also  lithographic  printing  with  great  ease. 

5.  The  detrimental  action  of  bleaching  powder  is 
done  away  with  by  my  process. 

These  properties  are  of  such  a  kind,  I  think,  as  to 
ensure  that  my  paper  will  be  very  much  used ;  and, 
moreover,  my  process  has  the  advantage  that  it 
allows  of  a  much  larger  number  of  sheets  being 
made  from  the  same  quantity  of  rags  than  in  the 
ordinary  method  of  paper-making;  for,  as  I  have 
already  said,  my  paper  is  decidedly  stronger  and 
tougher  than  much  thicker  paper  of  the  usual  kind. 
I  have  not  yet  ascertained  how  much  thinner  the 
waterproof  paper  may  be  than  ordinary  unprepared 


AND  SCHONBEIN  83 

paper  of  the  same  size  so  as  to  be  equally  tough ;  but 
it  is  certain  that  a  single  thickness  of  the  prepared 
paper  is  at  least  as  strong  as  a  double  thickness  of 
ordinary  paper. 

In  order  that  you  may  be  in  a  position  to  convince 
yourself  by  actual  observation  that  my  paper  does 
possess  these  properties,  I  have  taken  the  liberty  of 
enclosing  some  paper  strips.  Those  which  bear  the 
same  numbers  are  taken  from  the  same  sheet,  one 
being  prepared  and  the  other  in  its  natural 
condition.  If  you  put  the  strips  into  water,  you 
will  easily  be  able  to  distinguish  the  prepared 
paper  from  the  normal  paper  by  the  difference  in 
their  behaviour. 

It  seems  to  me  that  my  process,  which,  by  the 
way,  is  as  cheap  as  it  is  simple,  is  particularly 
adapted  for  preparing  printing,  packing,  and  wall- 
paper. As  enormous  quantities  of  paper  are  used 
for  these  purposes,  I  should  imagine  that  a  knowledge 
of  my  process  would  be  welcomed  by  paper-makers. 
I  therefore  venture  to  ask  you  whether  any  influential 
Swedish  paper-makers  would  be  inclined  to  put 
themselves  into  communication  with  me  with  a  view 
to  making  use  of  my  method,  or  whether  your 
Government  would  receive  instructions  concerning 
the  details  of  it,  in  the  interest  of  the  paper  industry 
of  the  country.  You  would  oblige  me  exceedingly 
if  you  would  kindly  give  an  answer  to  these 
questions. 

I  shall  shortly  send  you  a  full  account  of  the 
means  by  which  I  have  obtained  these  results,  and  of 


84  LETTEKS  OF  BEEZELIUS 

the  conclusions  of  my  recent  work  in  general  which 
may  perhaps  serve  as  a  communication  to  your 
Academy. 

The  transparent  parchment-like  leaf  is  modified 
vegetable  fibre,  which  I  can  prepare  in  any  required 
quantity. 

In  the  pleasant  anticipation  of  soon  receiving  an 
answer, 

I  have  the  honour  to  remain, 
With  the  utmost  respect,  my  dear  Baron, 
Yours  most  sincerely, 

C.  F.  SCHONBEIN. 

P,S. — The  unmarked  bit  of  paper  had  been  printed 
on,  and  the  printer's  ink  was  removed  by  potash.1 

BALE,  5th  March  1846. 


These  two  letters  of  Schonbein's  of  the  20th'  of  Sep-  ' 
tember  1845  and  the  5th  of  March  1846  also  remained 
unanswered,  at  least  there  is  no  reply  among  the  papers 
which  have  come  into  my  hands.  But  on  'the  8th  of 
April  following  Berzelius  gave  the  Academy  an  exhaustive 
account  6f  the  letter  of  March  the  5th,  in  which  he  also 
alludes  to  the  earlier  communication.  On  this  occasion 
he  once  more  referred  expressly  to  Marignac's  views  as  to 
the  nature  of  ozone. 

I  do  not  feel  quite  sure  whether  there  was  not  another 
letter  of  Schonbein's  which  is  now  lost,  coming  between, 
those  of  March  5th  and  June  20th.  His  expression  in 

1  Seven  different  samples  of  paper  are  attached  to  this  letter. 


AND  SCHONBEIN  85 

the  letter  of  June  20th  seems  to  me  to  indicate  this : 
"It  will  perhaps  interest  you  to  know  that  I  have  made 
many  experiments  with  my  guncotton."  This  alone  is 
enough  to  show  that  the  writer  assumes  on  the  part  of 
Berzelius  an  accurate  acquaintance  with  the  then  state  of 
affairs;  and  this  would  be  simply  and  easily  explained 
from  the  correspondence  which  they  were  usually  so  fond 
of  keeping  up.  Though  according  to  Schonbein's  own 
account  in  the  Allgemeine  Zeitung  of  25th  October  1846, 
the  first  experiments  with  guns  on  a  large  scale  had  been 
performed  in  the  week  April  6-12,  and  the  discovery 
had  attracted  the  attention  of  the  general  public  to  a 
very  unusual  degree,  Schonbein  had  given  a  public  lecture 
on  his  first  invention  for  the  first  time  as  late  as  May 
27th,  before  the  Scientific  Club  of  Bale.  In  this  lecture 
he  referred  directly  to  the  experiments  described  in  the 
letter  of  March  5th,  on  which  moreover  he  had  not 
lectured  to  the  Club  till  March  llth,  after  he  had  com- 
municated them  to  Berzelius.  So  if  Berzelius  knew  about 
the  experiments  with  guncotton  he  must  have  derived  the 
information  either  from  Schonbein  directly  or  from  notices 
in  the  papers,  for  the  scientific  journals  had  not  yet 
received  accounts  of  them  j  and  this  last  assumption 
seems  to  me,  as  I  have  said,  to  be  rendered  untenable  by 
the  expressions  which  Schonbein  employs. 


86  LETTEES  OF  BEKZELIUS 

XVIII 

Schonbein  to  Berzelius 

DEAR  SIR, 

I  hope  you  will  forgive  me  for  taking  the 
liberty  of  introducing  to  you  with  these  lines  two 
young  men  from  Bale,  Herr  Merian1  and  Herr 
Landerer,2  and  of  commending  them  to  your  favour- 
able notice.  They  are  going  to  travel  in  your 
beautiful  country  chiefly  for  artistic  purposes. 

You  will  perhaps  be  interested  if  I  take  this 
occasion  of  informing  you  that  I  have  just  recently 
performed  numerous  experiments  with  my  guncotton 
both  with  small  firearms  and  with  large  guns,  and 
I  have  obtained  the  most  satisfactory  results.  For 
instance  I  sent  a  shell  weighing  15  Ibs.  (7J  kgs.) 
1670  French  feet  from  a  mortar  with  one  ounce 
of  my  guncotton ;  and  with  half  a  drachm  (1*7  grms.) 
a  gun  sent  a  bullet  weighing  three-quarters  of  an 
ounce  several  inches  deep  into  wood  at  a  distance 
of  500  feet.  The  experiments  which  I  have  hitherto 
made  have  shown  that  one  pound  of  guncotton 
produces  at  the  very  least  as  much  effect  as  two 
pounds  of  the  best  gunpowder.  I  have  several  times 
used  my  guncotton  for  blasting  purposes  in  a  tunnel 3 

1  Eduard  Merian-Bischoff,  born  at  Bale  in  1824,  died  in  1859. 

2  He  became  a  painter  ;  he  was  murdered  at  Barbizon  near 
Paris  on  September  6th,  1893. 

3  The  tunnel  of  the  Baden  railway  near  Istein. 


AND  SCHONBEIN  87 

which  is  being  made  through  muschelkalk  in  our 
neighbourhood,  and  in  the  opinion  of  the  work- 
men it  was  as  effective  as  three  times  the  quantity  of 
powder. 

No  changes  need  be  made  in  the  guns,  cannon,  etc., 
in  order  to  employ  guncotton,  and  it  can  be  fired  by 
means  of  the  ordinary  percussion-caps.  Another 
useful  property  which  it  possesses  is  that  it  practically 
does  not  foul  or  heat  the  guns  at  all,  so  that  several 
hundred  charges  can  be  fired  from  the  same  gun 
without  its  having  to  be  cleaned. 

With  the  greatest  respect,  I  have  the  honour  to  be, 
My  dear  Baron, 

Yours  most  truly, 

C.  F.  SCHONBEIN. 
BALE,  20ta  June  1846. 


This  letter  was  laid  before  the  Academy  on  the  9th  of 
September  (the  cause  of  the  delay  is  explained  in  Ber- 
zelius'  answer),  together  with  a  communication  of  the  16th 
of  August  from  the  second  discoverer  of  guncotton,  Prof. 
Bb'ttger  l  of  Frankfort  on  Main,  and  another  from  Wohler 
of  Gb'ttingen,  and  was  printed  in  the  Ofversigt,  Arg.  3 
(1846)  p.  209. 

1  Kudolph  Bottger,  born  at  Aschersleben  in  1806,  died  at 
Frankfort  on  Main  in  1881.  In  August  1846,  when  professor 
at  the  Physical  Society  at  Frankfort,  he  independently  dis- 
covered guncotton,  and  joined  with  Schonbein  in  the  practical 
utilization  of  the  discovery. 


88  LETTEKS  OF  BEEZELIUS 

Eerzelius  answered  it  as  follows  : 


XIX 

Berzelius  to  Schonbein 

STOCKHOLM,  18th  November  1846. 

DEAR  SIR, 

The  letter  of  June  the  20th  with  which 
you  honoured  me  did  not  come  to  hand  till  the 
beginning  of  September.  Herr  Merian,  who  was  the 
bearer  of  it,  informed  me  that  he  was  to  deliver, 
along  with  it,  a  packet  of  specimens  of  paper  from 
you ;  this,  however,  he  had  left  at  Hamburg,  and  he 
was  unwilling  to  hand  over  the  letter  till  the  box  had 
come.  But  the  box  had,  together  with  the  rest  of  his 
luggage,  been  sent  to  Berlin,  whither  he  intended  to 
go  in  a  few  days.  I  requested  him  to  deliver  it  to 
our  minister  in  Berlin ;  this  he  failed  to  do,  although 
he  made  an  ascent  with  the  minister  in  Mr.  Green's 
balloon.  As  I  also  learned  from  him  that  you  had 
gone  to  England,  I  deferred  expressing  to  you  my 
gratitude  for  the  information  on  guncotton  till  I 
learnt  what  your  address  was.  I  am  now  sending  it 
to  London  on  the  chance  of  its  finding  you. 

Permit  me  to  convey  to  you  my  sincerest  congratu- 
lations on  this  interesting  and  significant  discovery, 
the  practical  nature  of  which  you  have  so  promptly 


AKD  SCHONBEIX  89 

appreciated.  Ever  since  Prof.  Otto  of  Brunswick1 
suggested  a  method  for  obtaining  guncotton,  this 
discovery  has  probably  kept  a  greater  number  of 
inquiring  minds  busy  than  any  other  in  the  field  of 
chemistry. 

I  also  have  been  engaged  in  experiments  .  on  it ;  I 
prepare  it  from  equal  parts  by  volume  of  concentrated 
sulphuric  acid  and  commercial  nitric  acid  of  specific 
gravity  145.  I  have  discovered  that  it  is  formed 
from  lignin,  and  can  be  produced  from  the  lignin  of 

1  Friedrich  Julius  Otto,  born  in  1809  in  Grossenhain  in 
Saxony,  from  1835  professor  of  chemistry  and  pharmacy  at  the 
Collegium  Carolinum  of  Brunswick,  where  he  died  in  1870. 
He  also  had,  as  he  asserted,  discovered  a  method  of  preparing 
guncotton,  founded  on  a  paper  by  Pelouze  ["  Note  sur  les  pro- 
duits  de  1'action  de  1'acide  nitrique  concentre"  sur  1'amidon  et  le 
ligneux,"  Gompt.  Rend.,  i.  7  (1838)  p.  713].  This  he  had 
published  in  the  daily  papers  in  October  1846,  first  in  the  All- 
gemeine  Zeitung  of  5th  October  1846  [reprinted  in  the  Journal 
fur  prakt.  Chemie,  vol.  xl.  (1847)  p.  194,  and  added  superfluous 
and  malicious  notes  directed  against  Schonbein's  legitimate 
efforts  to  turn  his  discovery,  the  enormous  practical  value  of 
which  he  had  instantly  perceived,  to  the  best  pecuniary  advan- 
tage. These  remarks  were  the  more  unjust  as  Schonbein  was 
actually  suffering  from  the  consequences  of  his  "  practical "  dis- 
covery. On  September  the  2nd,  1846,  he  writes  to  his  wife 
from  London :  "  Perhaps  I  may  make  something  of  it  if  I  do 
not  lose  patience,  but  this  is  not  easy.  In  certain  respects  it  is 
almost  a  misfortune  to  have  made  an  important  practical  dis- 
covery ;  it  completely  destroys  one's  peace  of  mind.  Faraday 
and  Grove  told  me  the  same  thing  :  they  continually  stood  in 
fear  of  coming  across  something  which  would  bring  them  in 
contact  with  the  practical  world,  as  I  have  done."  In  October 
he  writes  to  her  from  Stanmore  :  "  According  to  the  opinion  of 
experts  the  patent  is  in  no  danger  through  Otto's  articles.  The 
English  press  is  unanimous  in  criticizing  all  later  discoverers, 
and  saying  that  it  is  discreditable  to  these  men  to  deprive  me 
of  my  well-earned  deserts." 


90  LETTEES  OF  BEEZELIUS 

all  vegetable  matter,  especially  if  the  incrustation  is 
previously  removed  by  moistening  it  with  a  solution 
of  caustic  alkali.  I  have  prepared  it  from  Sphagnum 
palustre,  from  oakum,  from  straw,  and,  best  of  all,  from 
friable,  decaying  wood,  which,  when  the  humin  has 
been  extracted  by  alkaline  solutions,  yields  an  exquisite 
powdery  guncotton.  The  scientific  term  I  propose 
to  apply  to  it  is  lignin  nitrate,  since  a  body  got  from 
these  substances  cannot  well  be  called  guncotton. 

I  also  endeavoured  to  prepare  it  from  Cladonia 
rangiferina  and  Cetraria  islandica.  These,  however, 
contain  a  framework,  which  is  composed  not  of  lignin 
but  of  starchy  filaments,  and  yields  nothing  but 
amylin  nitrate,  i.e.,  xyloidin.  The  products  of  com- 
bustion of  lignin  nitrate  comprise  a  gas  which  I  think 
is  cyanogen,  which  I  certainly  had  not  looked  for 
among  them.  I  had  no  time  to  inquire  into  the  pre- 
cise elementary  structure  of  this  interesting  compound; 
I  dissolved  it  in  caustic  alkali,  in  which  it  is  readily 
soluble,  and  obtained  therefrom  saltpetre,  glucinic 
acid,  apoglucinic  acid  and  other  products,  which  were 
not  examined  further.  My  attempts  to  reproduce 
lignin  by  means  of  the  exchange  of  nitric  acid  for 
water  failed  conspicuously. 

You  would  greatly  oblige  'me  by  favouring  me  with 
the  results  of  your  further  investigations  on  the  appli- 
cation of  lignin  nitrate  as  an  explosive. 
I  have  the  honour  to  remain, 
With  the  greatest  respect, 

Your  most  obedient  servant, 

JAC.  BERZELIUS. 


AND  SCHONBEIN  91 


XX 

Schbnbein  to  Berzelius 

DEAR  SIR, 

Your  kind  note  of  November  of  last  year  has 
just  been  forwarded  to  me  from  England,  and  so  I 
hasten  to  thank  you  most  sincerely  for  it.  I  learned 
with  the  greatest  interest  the  results  you  obtained  with 
guncotton,  especially  as  I  also,  as  early  as  last  spring, 
made  experiments  not  only  with  cotton  but  also 
with  a  number  of  plants,  consisting  chiefly  of  lignin, 
and  obtained  explosive  substances  from  them. 

You  will  have  heard  that  last  year,  here  in  Bale  as 
well  as  in  England,  I  carried  out  many  experiments 
in  shooting  and  blasting  with  my  guncotton,  and  I 
should  like  now  to  give  you  some  details.  In 
Faversham  in  Kent  we  employed  a  very  accurately 
constructed  mortar,  which  throws  shells  of  sixty-four 
pounds  and  is  used  for  testing  the  powder  which  the 
factories  of  that  place  supply  to  the  British  Govern- 
ment. Two  ounces  of  the  best  English  powder  sent 
a  shell  of  sixty-four  pounds  from  this  mortar  on  an 
average  275  feet,  whereas  an  ounce  of  my  guncotton 
sent  the  same  shell  550  feet.  In  carbines  of  narrow 
calibre  10  grms.  of  guncotton  produced  the  same 
effect  as  41  grms.  of  the  best  gunpowder.  In  pistols 
of  a  particular  pattern  guncotton  exhibited  a  driving 
force  seven  times  as  great  as  that  of  gunpowder.  I 
made  numerous  experiments  in  blasting  in  the  mines 
and  slate  quarries  of  Kent  and  in  a  tunnel  in  our 


92  LETTEES  OF  BEBZELIUS 

neighbourhood  which  is  now  under  construction ;  all 
gave  most  satisfactory  results,  and  in  the  opinion  of 
the  engineers  present  proved  that  for  blasting  purposes 
guncotton  is  preferable  to  gunpowder.  One  part  of 
guncotton  is  under  these  circumstances  as  effective  as 
five  parts  of  powder.  In  many  instances  the  gun- 
cotton  produced  eight  and  ten  times  as  great  an 
effect  as  powder.  Although  I  experimented  almost 
daily  for  many  months  I  have  never  had  the  slightest 
accident  and  not  once  has  any  of  the  cannons,  mortars 
or  small  guns  from  which  many  hundreds  of  shots 
have  been  fired  under  my  direction,  exploded.  As  far 
as  my  own  observations  go  I  have  not  even  observed 
that  the  firearms  were  perceptibly  damaged  by  the 
guncotton.  I  once  caused  forty  shots  in  succession 
to  be  fired  from  an  American  carbine,  and  after  the 
experiment  it  was  as  clean  as  before.  I  find  it  con- 
venient to  saturate  my  guncotton  with  a  solution  of 
potassium  nitrate,  for  experience  shows  that  guncotton 
so  treated  is  more  readily  compressible,  without 
becoming  perceptibly  harder  to  explode.  Possibly 
this  film  of  potassium  nitrate  enveloping  the  explosive 
filament  makes  it  less  easy  to  explode  and  more 
uniform  in  action.  In  England  they  are  now  making 
arrangements  to  prepare  guncotton  on  a  large  scale, 
and  I  think  that  there  it  will  soon  be  widely  used  for 
blasting.  I  and  others  also  have  not  yet  given  up 
the  hope  that  guncotton  will  likewise  be  applicable 
for  purposes  of  war.  It  is  anything  but  honest  of 
the  French  to  continue  to  claim  priority  in  the 
discovery  of  guncotton  on  account  of  Bracconnot's 


AND  SCHONBEIN  93 

xyloidin  as  they  have  for  some  time  done,  especially 
as  they  subsequently  admitted  the  very  obvious 
difference  between  the  two  substances,  and  as  I 
prepared  guncotton  as  early  as  last  year.  I  had  no 
desire  to  assert  my  claims  before  the  French  Academy, 
because  I  am  convinced  that  impartial  men  of 
science  will  come  to  a  right  conclusion  on  this 
question. 

The  last  number  of  Poggendorff's  Annalen  contains 
a  few  papers  of  mine,  which  may  interest  you  inas- 
much as  they  indicate  the  facts  which  led  me  to  the 
discovery  of  guncotton.  The  resinous  substance 
which  is  formed  by  the  action  of  a  mixture  of  nitric 
and  sulphuric  acids  on  sugar  appears  to  be  a  substance 
quite  analogous  to  guncotton,  and  if  the  latter  is  lignin 
nitrate,  the  former  must  be  nitrate  of  sugar.  Possibly 
the  names  nitrolignin,  nitrosaccharine,  nitroamylin, 
etc.  would  be  suitable  for  such  compounds.  Since 
according  to  my  view  N05  does  not  exist,  I  con- 
sider that  the  compound  in  question  contains  ]N"04 
combined  with  an  organic  substance.  The  following 
fact  which  I  have  ascertained  appears  to  be  of 
especial  interest,  namely  that  flowers  of  sulphur 
treated  with  a  mixture  of  nitric  and  sulphuric  acids 
produce  sulphurous  acid  even  at  low  temperatures. 
Why  is  sulphuric  acid  not  formed  under  these  circum- 
stances ?  I  hold  the  unusual  view  that  the  sulphurous 
acid  formed  under  these  circumstances  is  a  secondary 
product,  derived  from  the  change  of  hydrogen  sulphide 
to  peroxide,  in  a  manner  analogous  to  the  formation 
of  sulphurous  acid  by  the  action  of  water  on  chloride 


94  LETTEES  OF  BEKZELIUS 

of  sulphur.  Furthermore  it  is  remarkable  that 
sulphurous  acid  brought  in  contact  with  the  mixture 
of  nitric  and  sulphuric  acids  is  not  converted  into 
sulphuric  acid,  as  takes  place  when  the  first  hydrate 
of  nitric  acid  alone  is  mixed  with  sulphurous  acid. 
I  think  these  reactions  deserve  the  undivided  attention 
of  chemists.  That,  according  to  my  experience,  ozone 
combines  with  iodine,  bromine  and  chlorine  to  form 
compounds  very  similar  to  those  which  these  three 
bodies  form  with  one  another,  is  also  a  fact  which 
may  not  be  without  importance. 

A  few  days  ago  I  was  most  agreeably  surprised  by 
receiving  the  Vasa  medal.  His  Majesty  the  King  of 
Sweden  has  by  granting  this  distinction  bestowed  on 
me  an  honour  of  which  I  am  hardly  worthy,  and  for 
which  I  feel  myself  deeply  indebted  to  him.  You 
would  be  doing  me  a  great  favour  if  you  would  kindly 
let  me  know  whether  I  should  express  my  humble 
thanks  for  this  distinction  in  a  letter  addressed  to 
His  Majesty  himself. 

I  trust  that  I  shall  soon  have  the  pleasure  of 
receiving  a  letter  from  you,  and  I  have  the  honour  to 
be,  with  the  greatest  respect, 

Your  obedient  servant, 

C.  F.  SCHONBEIN. 

BiLE,  12th  February  1847. 


AND  SCHONBEIN  95 

XXI 

Berzelius  to  Schbnbein 

STOCKHOLM,  \Wi  March  1847. 

DEAR  SIB, 

I  thank  you  sincerely  for  your  courteous 
letter  of  February  the  12th  and  for  the  interesting 
information  which  it  contains. 

I  congratulate  you  cordially  on  the  honour  be- 
stowed upon  you  by  our  king.  It  gave  me  great 
pleasure  to  hear  of  it.  His  Majesty  asked  me  what 
should  now  be  done  with  regard  to  your  proposal  to 
communicate  to  us  for  a  fixed  sum  the  details  of  the 
method  of  manufacturing  guncotton,  which  has  now 
been  made  public.  I  suggested  to  His  Majesty  that 
he  should  grant  to  the  discoverer,  whose  invention 
was  certain  to  be  profitable  to  us,  some  token  of  royal 
favour,  for  instance  the  honour  of  knighthood.  The 
king  replied  that  he  would  consider  the  matter.  A 
few  weeks  later  a  ceremony  of  investiture  was  held, 
at  which  you,  however,  were  not  mentioned,  although 
several  foreigners  were  named,  and  so  I  feared  that 
the  subject  had  been  overlooked,  till  I  was  most 
agreeably  surprised  to  learn  from  your  letter  that 
His  Majesty  had  not  forgotten  you. 

At  the  last  meeting  of  the  Academy  I  submitted 
your  last  letter  to  them. 


96  LETTEES  OF  BERZELIUS      - 

The  king  happened  to  be  present  at  the  Academy, 
and  to  your  memoranda  added  the  reports  on  gun- 
cotton  given  by  his  ministers  from  various  quarters, 
containing  among  other  things  a  statement  that  in 
Brunswick  serious  disasters  had  been  caused  by  the 
bursting  of  rifles  through  too  powerful  a  charge  of 
guncotton. 

Like  you  L.  Svanberg 1  has  prepared  compounds  of 
sugar  and  gum  with  a  mixture  of  nitric  and  sulphuric 
acids;  they  are,  however,  not  to  be  compared  to 
nitrolignin.  You  will  observe  that  I  have  adopted 
your  nomenclature;  lignin  nitrate  is  in  fact  a  mis- 
nomer, for  the  substance  which  unites  with  nitric 
acid  is  no  longer  lignin,  as  it  has  already  given  up 
several  atoms  of  hydrogen  and  oxygen. 

On  the  other  hand  I  am  unable  to  subscribe  to 
your  views  on  nitric  acid  and  the  nitrates.  They 
cannot  be  correct.  The  test  of  the  truth  of  a  theory 
is  that  it  should  harmonize  the  particular  instance 
with  the  whole  system  of  science ;  for  the  laws  of 
nature  are  always  consistent  with  one  another.  Now 
if  you  advance  a  principle  which  makes  an  exception 
of  what  was  before  consistent  with  scientific  ideas, 
logic  pronounces  against  you.  So  far  as  I  can  judge 
from  your  paper,  you  were  led  to  this  by  concluding, 
from  the  fact  that  ozone  and  nitric  acid  at  ordinary 

1  Lars  Friedrich  Svanberg,  born  in  Stockholm  in  1805,  was 
a  lieutenant,  then  teacher  of  chemistry  and  physics  at  the 
Military  College  at  Karlsberg.  From  1858  to  1874  lie  was 
professor  of  chemistry  at  Upsala,  where  he  died  in  1878.  "  Om 
salpetersyrans  forening  nied  nagra  Kroppar,"  Ofversigt,  Arg. 
4  (1847)  p.  51. 


AND  SCHONBEIN  97 

temperatures  oxidize  different  bodies  in  an  analogous 
manner,  that  therefore  the  oxidizing  constituent  of 
nitric  acid  must  be  ozone.  In  addition  to  this  you 
assume  that  ozone  is  a  compound  of  H  +  0,  isomeric 
with  hydrogen  peroxide,  and  so  nitric  acid  must  be 
H202  +  N204  and  the  nitrates,  E  N.  But  does  ozone 
really  contain  hydrogen  ?  This  question  we  can 
answer  most  emphatically  in  the  negative.  If  oxygen 
gas  collected  during  the  last  third  of  its  evolution 
from  potassium  chlorate  be  exposed  to  a  series  of 
short  electric  sparks,  ozone  is  formed  just  as  readily 
and  to  precisely  the  same  extent  as  during  the  first 
third  of  the  operation.  In  this  case,  however,  it  is 
physically  impossible  for  water  to  be  present.  This 
constitutes  the  most  indisputable  proof  that  ozone 
does  not  contain  hydrogen.  Hence  it  follows  that 
ozone  is  an  allotropic  modification  of  oxygen  itself, 
distinguished  from  the  ordinary  form  by  the  sensation 
it  produces  in  the  olfactory  nerves  and  its  power  of 
entering  into  all  manner  of  combinations  at  low 
temperatures ;  thus  ozone  is  entitled  to  an  infinitely 
greater  attention  than  if  it  were  an  individual  sub- 
stance. From  this  point  of  view  your  discovery  of 
ozone  is  one  of  the  most  magnificent  ever  made ;  but 
you  should  not  allow  yourself  to  be  dazzled  by  it. 

Starting  from  this  simple  assumption,  which  is 
now  established,  we  have  to  ask  what  connection 
there  is  between  ozone  and  hydrogen  peroxide,  the 
acids  of  nitrogen,  chlorine,  bromine,  iodine,  etc. 
Ozone  oxidizes  at  low  temperatures  and  unites  with 
organic  bodies  to  form  derivatives  which  ordinary 


98  LETTERS  OF  BERZELIUS 

oxygen  is  incapable  of  producing,  as  the  latter  only 
becomes  active  at  temperatures  at  which  the  organic 
substances  are  destroyed.  The  acids  I  have  mentioned 
also  produce]this  effect ;  they  all  give  rise  to  oxygen 
compounds  at  low  temperatures.  This  shows  that 
hydrogen  peroxide  is  not  present  in  nitric  acid.  The 
theory  explains  the  formation  of  ozone  by  lightning, 
by  frictional  electricity,  and  by  hydro-electricity. 
Its  production  by  means  of  phosphorus  then  appears 
of  a  purely  catalytic  nature,  which  is  quite  conceiv- 
able: whereas  it  is  not  conceivable  that  so  readily 
oxidizable  a  body  as  phosphorus,  which  itself  absorbs 
oxygen,  should  yield  so  unstable  an  oxidation  product 
of  hydrogen  as]hydrogen  peroxide.  I  trust  you  will 
excuse  my  preaching,  and  not  refuse  to  learn.  Soon 
you  will  find  how  the  shadows  are  dispersed  by  the 
light  of ^correct  ideas. 

Address  your  letter  of  acknowledgment  to  the 
Foreign  Secretary,  His  Excellency  Baron  A.  Ihre. 
It  is  quite  proper  to  enclose  in  it  a  message  in  an 
envelope,-  which,  however,  should  not  be  sealed, 
addressed  to  His  Majesty  the  King,  and  to  inquire  of 
the  Minister  whether  he  considers  the  letter  suitable 
to  be  delivered  to  His  Majesty.  This  letter,  however, 
is  not  essential ;  you  need  only  request  the  Minister 
to  convey  to  His  Majesty  your  respectful  thanks ; 
but  perhaps  it  might  not  be  unwelcome  to  His 
Majesty^to  receive  a  short  letter  from  you. 
Farewell. 

Yours  sincerely, 

JAC.  BERZELIUS. 


AND  SCHONBEIN  99 


XXII 
Schonbein  to  Berzelius 

DEAE  SIR, 

I  thank  you  sincerely  for  your  kind  and 
interesting  letter  of  the  13th  inst.  I  have  followed 
the  advice  you  were  so  good  as  to  give  me  and  have 
sent  a  letter  of  thanks  to  His  Majesty  the  King,  as 
well  as  to  His  Excellency  the  Foreign  Secretary. 
Permit  me  in  this  matter  to  express  to  you  my  sincere 
thanks  for  having  obtained  for  me  by  your  good 
offices  so  honourable  a  distinction. 

I  can  hardly  assent  to  your  and  de  la  Rive's  views 
on  the  nature  of  ozone,  although  I  readily  admit  and 
have  long  been  aware  that  they  make  it  out  to  be 
a  substance  of  infinitely  greater  interest  than  it 
appears  according  to  my  theory;  for  this  reason  I 
wrote  to  de  la  Rive  a  short  time  ago :  "  For 
ambition's  sake  I  must  wish  that  you  and  Berzelius 
are  in  the  right,  and  Mr.  Schonbein  in  the  wrong, 
for  ozone  being  mere  oxygen  modified  by  electricity, 
would  be  a  substance  infinitely  more  interesting  than 
my  peroxide  of  hydrogen." l  My  reasons  for  rejecting 
your  view  are  as  follows:  1.  Not  a  single  fact  is 
known,  which  shows  that  any  elementary  body  is 
changed  in  any  way  whatever  in  its  properties  by 
means  of  electricity.  2.  On  the  other  hand  there  are 
a  number  of  substances  which  by  combining  with 
1  This  sentence  is  in  English  in  the  original. — Tr. 


100  LETTEES  OF  BEEZELIUS 

oxygen  modify  it  in  such  a  way  that  it  unites  at 
ordinary  temperatures  with  many  bodies,  on  which 
pure  oxygen,  under  the  same  conditions,  has  no  action. 
Such  substances  are  for  example  HO,  PbO,  MnO, 
AgO,  which,  when  they  combine  with  oxygen,  so 
change  it  that  it  decomposes  potassium  iodide, 
converts  -potassiuiq  ferrocyanide  into  fsrricyanide, 
colours  guaiacum  resin  blue,  etc. ;  in  other  words  it 
acts  like  ozone.  3.  When  exposed  to  the  action  of 
electric  sparks  for  some  time  oxygen  gas  prepared 
from  melted  potassium  chlorate  does,  it  is  true,  turn 
starch  paste  containing  potassium  iodide  blue,  and 
affects  the  organs  of  smell,  but  it  is  not,  according 
to  my  experiments,  dissolved  to  any  great  extent 
by  solutions  of  potassium  iodide  or  potassium  ferro- 
cyanide, or  oxidizable  metals ;  and  the  residual  gas 
behaves  like  ordinary  oxygen.  Now  I  should  think 
that  a  cubic  inch  of  dry  oxygen  gas  if  exposed  for  a 
sufficient  length  of  time  to  the  electric  current, 
would  be  completely  ozonized,  and  thus  be  entirely 
taken  up  by  the  abovementioned  solutions. 

4.  But  infinitesimal  traces  of  water  vapour,  such 
as  might  be  present  in  oxygen  supposed  to  be  dry, 
suffice  to  produce  a  perceptible  quantity  of  ozone,  and 
so  it  seems  to  me  that  some  such  view  as  mine  is 
less  improbable  than  yours.  5.  The  destruction  of 
ozone  on  heating  is  readily  explained  by  the  assump- 
tion that  at  higher  temperatures  it  is  split  up  into 
water  and  oxygen,  like  so  many  other  superoxides, 
especially  The'nard's  oxidized  water.  According  to 
your  view  we  must  assume  that  heat  restores  the 


AND  SCHONBEIN  101 

ozonized  oxygen  to  its  ordinary  condition.  More- 
over it  would  be  strange  if  heat,  which  as  a  rule 
increases  the  chemical  activity  of  oxygen,  should 
produce  the  opposite  effect  on  ozone.  6.  In  dry  air 
phosphorus  has  not  the  power  to  produce  ozone  in 
appreciable  quantities,  but  it  forms  it  the  more 
abundantly,  the  more  moisture  is  present. 

With  regard  to  the  formation  of  ozone  by  means  of 
phosphorus,  it  appears  to  me  that  this  fact  is  equally 
remarkable  whether  we  assume  the  former  to  be 
modified  oxygen  or  peroxide  of  hydrogen,  for  finely 
divided  phosphorus  shaken  up  with  an  atmosphere  of 
ozone  immediately  destroys  the  latter.  The  forma- 
tion of  ozone  in  the  presence  of  phosphorus  must 
strike  us  as  equally  strange  whether  we  assume  that 
by  means  of  catalysis  modified  oxygen  or  gaseous 
hydrogen  peroxide  is  formed,  for  the  former  should 
be  absorbed  by  phosphorus  just  as  readily  as  the 
latter  should  lose  its  active  oxygen.  I  would  take 
this  opportunity  of  drawing  your  attention  to  the 
behaviour  of  ozone  towards  iodine,  bromine  and 
chlorine.  The  compound  formed  when  paper  charged 
with  iodine  is  held  in  an  atmosphere  strongly  charged 
with  ozone,  is  so  like  chlorine,  that  it  shows  almost 
all  the  properties  of  the  latter.  It  is  not  an  acid,  but 
on  treatment  with  water  it  is  converted  into  iodic 
acid  and  iodine.  Similarly  bromine  and  chlorine 
water,  which  have  absorbed  large  quantities  of  ozone, 
are  by  no  means  acid,  i.e.,  they  do  not  contain  chloric 
or  bromic  acid.  The  same  substance  which  ozone 
forms  with  iodine  seems  also  to  result  when  strips 


102  LETTEES  OF  BERZELIUS 

of  iodine  paper  are  exposed  to  moist  atmospheric 
air  saturated  with  nitrous  acid  vapours,  or  suspended 
in  a  flask,  the  bottom  of  which  is  covered  with  a 
mixture  of  water  and  nitrous  acid. 

I  suspect  that  there  exists  a  compound  consisting 
of  N02-fH02,  which  when  it  comes  in  contact  with 
iodine  gives  up  to  it  its  H02.  According  to  your 
view  we  must  assume  that  when  ozonized  oxygen 
combines  with  iodine,  bromine  and  chlorine  it  is  as 
ozone  that  it  does  so. 

With  regard  to  my  views  on  the  hydrate  of  nitric 
acid,  I  venture  to  maintain  that  it  is  by  no  means 
isolated  and  without  analogy,  so  long  as  one  holds 
similar  views  on  other  acids.  Anhydrous  sulphuric 
acid  for  example  I  regard  as  S02  +  0,  the  third 
atom  of  oxygen  being  in  a  chemically  active  state ; 
the  hydrate  of  sulphuric  acid  I  look  upon  as 
S02+H02,  and  the  normal  sulphates  as  S02+E02; 
the  hydrate  of  chloric  acid  would  of  course  be 
C104+H02,  anhydrous  iodic  acid  I04+0  etc. 
Possibly  we  might  also  regard  the  so-called  first 
hydrate  of  oxalic  acid  as  2CO-fH02,  acetic  acid  as 
C4H4  +  20  or  as  C4H3  +  H02.  However,  I  am  always 
suspicious  about  substances  which  cannot  be  isolated 
and  which  cannot  exist  except  in  combination  with 
other  substances,  such  as  water  and  the  so-called  salt- 
bases.  I  am  half  inclined  to  fear  that  the  assumption 
of  these  hypothetical  compounds  has  retarded  rather 
than  promoted  the  progress  of  chemistry. 

I  have  taken  the  liberty  of  giving  you  some  of  my 
views  on  the  different  conditions  of  oxygen  in  the 


AND  SCHONBEIN  103 

pages1  which  I  enclose,  and  of  submitting  them  to 
your  judgment.  Should  you  consider  them  in  any 
way  as  worthy  of  your  attention,  I  trust  you  will  be 
kind  enough,  when  you  have  an  opportunity,  to  send 
me  a  few  comments  on  them.  Finally  I  must  ask 
you  to  do  me  a  great  favour.  As  the  patent  which 
I  have  taken  out  for  my  guncotton  in  England  will 
undoubtedly  be  contested,  I  should  be  very  much 
obliged  to  you  if  you  would  state  in  a  letter,  in  what- 
ever manner  you  consider  most  suitable,  that  it  was 
I  who  first  discovered  and  prepared  nitrolignin. 
Such  an  expression  of  your  opinion  would  have  great 
weight  in  England,  and  I  have  little  doubt  that  you 
also  will  ascribe  to  me  the  priority  in  this  matter.  I 
at  any  rate  consider  that  I  have  a  full  claim  to  it. 
With  the  sincerest  hope  that  your  valuable  life  may 
be  spared  to  Science,  I  remain, 

With  the  greatest  respect, 

Yours  respectfully, 

C.  F.  SCHONBEIN. 
BALE,  29th  March  1847. 


The  letter  of  Berzelius  no  doubt  suggested  to  a  certain 
extent  a  discourse  of  Schonbein's :  "  On  various  Chemical 
States  of  Oxygen,"2  which  he  delivered  on  21st  April  to 
the  Scientific  Club  of  Bale,  and  in  which  he  attacks  the 
views  of  Marignac,  de  la  Rive,  and  Berzelius.  [cf.  Poggend. 
Annal.,  vol.  Ixxi.  (1847)  p.  517  ;  where  he  uses  the  words  : 
"  since  the  great  Swedish  chemist  assails  me  in  writing  "]. 

1  See  Appendix.  2  Ibid. 


104  LETTEKS  OF  BEEZELIUS 

Berzelius  does  not  himself  seem  to  have  given  any 
summary  of  this  work,  for  the  passage  in  the  Jdhresbericht 
for  1848,  *  which  treats  of  this  paper,  says  with  respect  to 
Schonbein's  attempt  to  draw  a  parallel  between  ozone  and 
chlorine,  bromine  and  iodine,  and  thus  to  represent  them 
as  "  oxylizations  "  of  radicals  not  yet  isolated  :  "  all  very 
similar  to  views  held  thirty  or  forty  years  ago."  2  Berzelius, 
the  faithful  adherent  of  the  Murium  theory,  could  not 
have  written  thus.  This  view  of  mine  is  further  con- 
firmed by  the  fact  that  it  can  be  proved  that  the  report  of 
Schonbein's  other  work,  for  instance,  on  guncotton,8  for 
which,  as  we  have  seen,  Berzelius  evinced  so  great  an 
interest,  was  no  longer  drawn  up  by  Berzelius  himself,  but 
by  Lars  Svanberg.  Consequently  we  may  regard  as  the 
last  utterance  of  Berzelius  on  Schbnbein  and  his  work  a 
passage  to  be  found  in  the  27th  volume  of  the  Jahresbericlity 
which  runs  as  follows  : 

"  Assuredly  there  is  at  present  no  chemical  investiga- 
tion so  important  and  so  much  wanted  by  the  scientific 
world  as  a  systematic  memoir  of  the  history  of  ozone  in  all 
its  details.  Certainly  no  work  would  yield  such  unexpected 
results  to  any  man  who  had  the  courage  to  undertake  it  in 
earnest,  and  who  did  not  try  to  avoid  the  difficulties  by 
means  of  vague  phrases,"  4  a  practice  to  which  Schonbein 
was  certainly  not  given. 

On  a  sheet  of  paper  in  part  filled  with  a  draft  of  a  letter 
to  Faraday  which  bears  the  address  Rotzberg,  near  Stans- 
stad,  but  no  date,  I  have  discovered  the  first  hasty  sketch 
of  an  obituary  notice  of  Berzelius,  which,  as  the  last 
remark  of  Schonbein  on  his  great  colleague,  may  well  have 

1  "  Jahresbericht  iiber  die  Fortschritte  der  Chemie"  continued 
after  the  death  of  Berzelius  by  L.  Svanberg.    Presented  to  the 
Swedish    Academy   of    Science    on  31st  March  1848.     [But 
Berzelius  did  not  die  till  7th  August  1848.] 

2  Loc.  cit.  p.  1 2.          3  Loc.  cit.  p.  342.  4  Loc.  cit.  p.  29. 


AND  SCHONBEIN  105 

a  place  here,  although  it  is  unfinished.  Whether  it  was 
ever  completed,  or  ever  printed,  I  am  unable  to  say,  as  I 
have  found  nothing  in  any  of  the  available  journals  with 
which  Schonbein  usually  kept  up  an  active  correspondence : 
Allgemeine  Zeitung,  Morgenblatt  fur  die  geUldeten  Stande, 
and  the  Easier  Zeitung,  which,  as  a  local  paper,  must  also 
be  taken  into  account.  An  obituary  notice  in  No.  237 
of  the  Allgemeine  Zeitung  of  24th  August  1848  is  plainly 
not  by  Schonbein. 

So  far  as  I  can  read  this  hardly  legible  writing,  the  last 
words  of  Schonbein  on  Berzelius  are  as  follows  : 

"Jakob  Berzelius  is  dead;  his  loss  will  be  deeply 
mourned  wherever  science  is  cherished  and  esteemed ; 
for  not  only  are  we  entitled  to  rank  him  with  the  most 
eminent  natural  philosophers  of  the  age,  but  he  was 
beyond  doubt  the  first  of  all  chemists  that  ever  lived. 
The  lofty  position  which  chemistry  occupies  to-day  is  due 
to  his  investigations,  which  are  as  numerous  and  as 
accurate  as  they  are  full  of  genius ;  and  without 
exaggeration  we  may  say  that  he  has  done  more  for  the 
advancement  of  science  than  all  other  chemists  together. 
The  greatest  and  most  brilliant  service  which  he  rendered 
consists  in  establishing  the  law  of  the  definite  proportions 
in  which  the  elements  combine  with  one  another,  a  work 
the  enormous  extent  and  significance  of  which  only  an 
expert  can  appreciate. 

"  Like  all  truly  great  scholars  he  was  devoid  of  petty 
conceit  and  jealousy,  and  with  an  impartiality  as  great  as 
his  knoAvledge  he  gave  due  recognition  to  the  labour  of 
others,  so  that  the  whole  chemical  world  gladly  accepted 
his  verdict." 

With  this  estimate  of  Berzelius  by  Schonbein  I  will 
conclude.  The  opinions  which  we  have  heard  the  two 
men  express  in  their  letters  reflect  as  much  honour  on  the 
one  as  on  the  other. 


APPENDIX 


ON  VARIOUS  CHEMICAL  STATES  OF 
OXYGEN 

ONE  of  the  most  important  and  interesting  branches  of 
chemical  investigation  to  which  it  would  seem  sufficient 
attention  has  not  been  devoted  is  the  influence  exerted 
on  the  affinity  of  a  substance  by  the  other  substances 
with  which  it  is  combined.  In  many  cases  the  same 
element  in  an  isolated  condition  shows  an  essentially 
different  behaviour  towards  certain  substances  from  that 
which  it  exhibits  when  in  combination.  In  this  con- 
nection oxygen  of  all  simple  bodies  shows  the  most 
remarkable  behaviour ;  for  according  as  it  is  isolated,  or 
in  this  or  that  state  of  combination,  it  may  show  either  a 
very  high  degree  of  chemical  activity  or  none  at  all, 

If  I  am  not  mistaken  there  is  no  single  element  with 
which  dry  oxygen  combines  at  ordinary  temperatures; 
but  when  it  is  united  with  certain  substances  its  be- 
haviour is  wholly  different.  Contrary  to  what  theoretical 
considerations  would  lead  us  to  expect,  combined  oxygen 
shows  such  a  degree  of  chemical  activity  that  even  at  low 


APPENDIX  107 

temperatures  it  forms  chemical  compounds  with  a  series 
of  bodies,  on  which  free  oxygen  under  conditions  other- 
wise the  same  has  no  action  whatever.  Among  the 
substances  which  by  their  union  with  oxygen  raise  its 
chemical  activity  are  several  oxides  of  the  general  formula 
RO,  such  as  HO,  PbO  and  MnO.  When  one  of  these 
oxides  combines  with  a  further  atom  of  oxygen  bodies  are 
formed  which  have  a  remarkable  power  of  oxidation ;  for 
example,  they  expel  iodine  from  potassium  iodide,  convert 
the  yellow  prussiate  of  potash  into  the  red,  turn  guaiacum 
solution  blue,  and  destroy  indigo  solution.  These  com- 
pounds also  resemble  one  another  in  their  voltaic  be- 
haviour; they  possess  a  remarkable  degree  of  electro- 
motive power,  i.e.,  they  are  eminently  electro-negative. 
The  peroxides  owe  all  these  properties  to  their  second 
atom  of  oxygen.  "We  must  therefore  assume  that  this 
second  atom  is  in  an  essentially  different  condition  from 
the  first.  It  seems  to  me  that  it  would  be  desirable  for 
science  to  possess  a  term  to  distinguish  the  chemically 
active  oxygen  in  such  a  compound ;  perhaps  we  might  use 
the  expression  "  oxylized,"  by  which  I  understand  oxygen 
which  has  a  tendency  to  leave  the  substance  with  which 
it  is  united  in  order  to  attach  itself  to  some  other  oxidiz- 
able  body.  Perhaps  it  would  also  be  convenient  to  use 
a  special  symbol  such  as  0  to  denote  the  oxylized  atom  of 
oxygen  in  a  compound.  The  peroxides  of  hydrogen,  lead 
and  manganese  would  accordingly  receive  the  formulae 
HO,  PbO  Mn6.  • 

As  is  well  known,  nitric  oxide  (N02)  exerts  a  very 
peculiar  influence  on  the  two  atoms  of  oxygen  which 
combine  with  it  to  form  nitrous  acid.  The  condition  of 
the  two  oxygen  atoms  combined  with  N02  is  not  the 
same  as  that  of  the  second  atom  of  oxygen  in  the  per- 


108  APPENDIX 

oxides  mentioned  above  ;  for  anhydrous  nitrous  acid  does 
not  act  even  on  readily  oxidizable  bodies  to  any  great 
extent  at  ordinary  temperatures,  and  can  sustain  a  high 
temperature  without  suffering  decomposition.  However, 
these  two  oxygen  atoms  can  without  difficulty  be  con- 
verted into  the  true  oxylized  state  by  mixing  the  nitrous 
acid  with  HO.  I  have  endeavoured  to  prove  that  the 
hydrate  of  nitric  acid  is  N04  +  H02,  and  that  a  compound 
of  the  formula  N02  +  H02  also  exists  ;  both  are  formed 
on  mixing  N04  with  HO  ;  the  water,  reducing  a  part  of 
the  N04  to  N02,  is  itself  converted  into  H02,  and  this 
peroxide  combines  partly  with  N04  and  partly  with  X02, 
according  to  the  following  equation  : 


4  +  2HO  =  (N04  +  H02)  +  (N02  +  H02). 


The  oxidizing  effects  which  these  two  bodies  produce 
at  the  ordinary  temperature  are,  in  my  opinion,  due  to 
the  oxylized  oxygen  contained  in  their  H02  ;  since  N04 
binds  H02  more  closely  than  N02  does,  K02  +  H02  is  a 
more  effective  oxidizing  agent  than  N04  +  H02;  hence 
the  former  even  when  diluted  with  ever  so  much  water 
decomposes  potassium  iodide,  potassium  ferrocyanide,  and 
hydrogen  sulphide  with  the  liberation  of  N02,  whereas 
very  dilute  nitric  acid  is  unable  to  produce  this  effect. 

As  to  chlorine,  bromine  and  iodine,  I  regard  them,  in 
accordance  with  the  older  theories,  as  peroxides  of  murium, 
bromium  and  iodium,  my  opinion  being  that  they  contain 
one  atom  of  oxygen  in  the  oxylized  condition,  to  which 
the  remarkable  oxidizing  actions,  which  these  bodies  are 
capable  of  producing  at  the  ordinary  temperature,  must 
be  ascribed.  Therefore  I  regard  the  oxides  of  murium, 
bromium  and  iodium  as  analogous  to  those  of  water, 


APPENDIX  109 

manganese  and  lead,  etc.,  and  ascribe  to  them  the  power 
of  oxylizing,  not  only  one  equivalent  but  the  whole  of  the 
oxygen  with  which  they  combine. 

A  peculiar  interest  attaches  to  the  relations  which  exist 
between  chlorine,  bromine  and  iodine,  the  peroxides,  and 
the  so-called  hydracids  of  the  halogens.  The  first  class 
of  substances  show  a  great  similarity  in  their  voltaic  and 
chemical  behaviour,  a  similarity  which  would  lead  anyone 
who  studied  them  without  regard  to  the  current  hypo- 
theses to  believe  that  they  had  a  similar  chemical  constitu- 
tion ;  this,  however,  is  completely  contrary  to  our  present 
ideas.  What  strikes  me  as  especially  remarkable  is  the 
following  :  When  the  hydracids  of  these  three  halogens 
are  mixed  with  the  peroxides,  chlorine,  bromine  and  iodine 
are  liberated  ;  furthermore  it  is  well  known  that  chlorine, 
for  example,  partially  converts  lead  oxide  into  lead  per- 
oxide. In  fact  it  is  not  improbable  that  chlorine  is  able, 
when  in  contact  with  water,  to  produce  some  hydrogen 
peroxide.  Moreover  we  know  that  concentrated  nitric 
acid  immediately  liberates  chlorine  from  hydrogen  chloride, 
and  my  latest  investigations  have  shown  that  even  a  very 
dilute  solution  of  nitrous  acid,  when  added  to  hydro- 
chloric acid,  at  once  sets  chlorine  free.  My  hypothesis 
compels  me  to  explain  all  these  phenomena  in  a  different 
way  from  that  in  which  they  are  explained  by  our  present 
theories.  When  aqueous  rnurium  oxide  is  brought  in 
contact  with  a  compound  containing  oxylized  oxygen, 
such  as  lead  peroxide,  a  part  of  the  murium  oxide  unites 
with  the  oxylized  oxygen  to  form  murium  peroxide, 
while  the  remainder  of  the  murium  oxide  or  hydrochloric 
acid  combines  with  the  lead  oxide  to  produce  the  so-called 
lead  chloride.  Conversely  when  murium  peroxide  is 
made  to  react  with  lead  oxide,  a  portion  of  the  latter  will 


110  APPENDIX 

unite  with  the  oxylized  oxygen  of  the  former  to  form  the 
peroxide,  whereas  another  portion  of  the  lead  oxide 
combines  with  murium  oxide  to  form  lead  chloride. 
Hydrochloric  acid,  in  contact  with  concentrated  nitric 
acid  takes  up  6  from  N04  +  fi6,  being  oxidized  to  Mu6, 
and  this  most  probably  unites  with  N04  to  form  an 
unstable  compound,  which  constitutes  the  oxidizing  agent 
in  aqua  regia.  The  action  of  murium  oxide  on  N02  4-  A  6 
differs  only  in  that  the  evolution  of  chlorine  takes  place 
with  greater  ease.  When  electric  sparks  are  passed 
through  a  mixture  of  gaseous  hydrochloric  acid  and  oxygen, 
chlorine  and  water  are  produced,  as  is  well  known. 
According  to  my  observations  electricity  determines  the 
combination  of  murium  oxide  with  oxygen,  and  the  latter, 
by  uniting  with  the  oxide,  is  transformed  into  the  oxylized 
state.  When  a  mixture  of  water  vapour  and  oxygen  gas 
is  subjected  to  the  same  electrical  treatment,  a  hydrogen 
peroxide  is  formed,  namely  ozone,  and  if  the  oxides  of 
lead,  manganese,  silver,  etc.,  were  capable  of  existing  in 
the  gaseous  form  they  would,  when  mixed  with  oxygen, 
undoubtedly  be  transformed  into  their  peroxides  011 
passing  electric  sparks  through  them.  Lead  hydroxide 
held  before  a  point  from  which  electricity  is  escaping  into 
moist  oxygen  or  atmospheric  air  is,  it  is  true,  according  to 
my  experiments,  changed  into  its  peroxide ;  this  is,  how- 
ever, due  to  a  secondary  reaction  produced  by  the  ozone 
which  is  formed  under  these  circumstances. 

With  regard  to  the  chemical  nature  of  ozone,  the 
highest  authority  on  chemical  questions  now  shares  the 
view  first  brought  forward  by  de  la  Kive,  that  ozone  is 
nothing  but  oxygen  modified  by  electricity,  and  that  it 
does  not  contain  hydrogen.  These  chemists  support  their 
view  by  the  fact  that  electric  sparks  passed  through 


APPENDIX  111 

oxygen,  prepared  from  melted  potassium  chlorate,  produce 
ozone.  I  am,  however,  unable  to  assent  to  this  view  for 
reasons  which  I  have  explained  elsewhere,  chiefly  because 
there  is  not  a  single  fact  to  show  that  electricity  is  capable 
of  changing  in  any  way  the  chemical  properties  of  any 
elementary  substance  whatever.  If  oxygen  is  capable  of 
undergoing  so  extraordinary  a  chemical  change  under  the 
influence  of  electricity,  this  is  a  case  perfectly  unique,  to 
which  there  is  not  even  the  remotest  analogy  to  be  found 
in  the  whole  sphere  of  chemistry.  On  the  other  hand  a 
large  number  of  cases  are  known  which  prove  conclusively 
that  oxygen,  when  united  to  certain  substances,  acquires 
so  great  a  degree  of  chemical  activity  that  it  oxidizes  even 
at  ordinary  temperatures,  and  this  analogy,  it  seems  to  me, 
is  more  in  favour  of  my  theory  as  to  the  nature  of  ozone 
than  of  those  proposed  by  others.  Therefore  I  am  firmly 
convinced  that  the  assumption  that  oxygen  prepared  from 
melted  potassium  chlorate  still  contains  traces  of  water  is 
less  bold  than  the  view  that  ozone  is  an  allotropic  modifica- 
tion of  ordinary  oxygen.  As  I  have  already  stated,  I  shall 
give  up  my  theory  and  accept  the  one  which  I  now 
dispute  so  soon  as  anybody  succeeds  in  transforming 
into  ozone  by  means  of  electricity  a  single  cubic  inch  of 
really  dry  oxygen.  However,  I  may  be  wrong,  and  the 
view  of  Berzelius  and  de  la  Kive  may  be  correct.  In 
that  case  we  should  have  to  assume  that  the  oxylization 
which  a  number  of  substances  can  produce  in  oxygen 
by  combining  with  it  can  also  be  produced  by  electricity 
alone,  and  furthermore  that,  for  example,  the  second 
oxygen  atom  of  the  normal  peroxides  exists  in  these 
compounds  as  ozone,  or  that  ozone  and  oxylized  oxygen 
are  one  and  the  same  substance.  Then  we  should  have 
also  to  assume  that  heat  could,  under  suitable  conditions, 


112  APPENDIX 

reconvert  oxylized  into  ordinary  oxygen,  since  isolated 
ozone  is  changed  by  heat  into  ordinary  oxygen  just  as 
the  peroxides  are  reduced  to  the  oxides  under  the  same 
conditions,  the  oxygen,  thus  separated,  appearing  in  its 
normal  condition,  and  as  the  first  hydrate  of  nitric  acid 
splits  up  into  N02,  HO  and  0.  The  separation  of  a 
portion  of  nitric  acid  would  in  that  case  be  due  to  the  fact 
that  only  a  definite  amount  of  ordinary  oxygen  is  capable 
of  uniting  with  H,  Pb,  Mn,  etc.  If  6  in  PbO  is  con- 
verted into  0  by  the  action  of  heat,  then  the  oxygen 
would  split  off,  for  PbO  can  remain  united  with  6  but 
not  with  0.  According  to  the  nature  of  the  compound 
RO,  with  which  0  is  combined,  it  requires  a  smaller  or 
greater  amount  of  heat,  to  effect  this  change  of  0  into  0, 
or  its  separation  from  KO. 

In  the  case  of  HO  this  change  takes  place  at  moderate 
temperatures,  whereas  lead  peroxide  requires  a  greater 
heat  and  MuO  a  still  greater. 

As  far  as  chlorine,  bromine  and  iodine  are  concerned — 
regarding  them  as  peroxides — the  highest  temperatures 
which  we  have  as  yet  succeeded  in  producing  are  as 
incapable  of  changing  their  0  into  0  as  they  are  of  melting 
charcoal  or  of  decomposing  a  substance  which  is  not  a 
compound.  If,  however,  these  peroxides  are  mixed  with 
substances  which  combine  either  with  their  oxide  or  with 
their  oxylized  oxygen,  then  the  decomposition  takes  place 
with  the  greatest  ease. 


'  '     -  5 

OF  THE 

{   UNIVERSITY  ] 

OF 


THIS  BOOK  IS  DUE  ON  THE  LAST  DATE 
STAMPED  BELOW 


AN  INITIAL  PINE  OF  25  CENTS 

WILL  BE  ASSESSED  FOR  FAILURE  TO  RETURN 
THIS  BOOK  ON  THE  DATE  DUE.  THE  PENALTY 
WILL  INCREASE  TO  SO  CENTS  ON  THE  FOURTH 
DAY  AND  TO  $1.OO  ON  THE  SEVENTH  DAY 
OVERDUE. 


FEB  24 


I2Dec'58CS! 


LD  21-95m-7,'37 


